
Glass J^ 
Bock_K3i 



w\n 



AN 



INTRODUCTION TO THE STUDY 



Compounds of Carbon; 



OEGAjSTIO ohemistey. 



BY 

IRA REMSEN, 

PROFESSOR OF CHEMISTRY IN THE JOHNS HOPKINS UNIVERSITY. 






BOSTON, U.S.A.: 
D. C. HEATH & COMPANY. 

1897. 



m7 



■% 



Entered according to Act of Congress, in the year 1885, by- 
IRA REMSEN, 
in the Office of the Librarian of Congress, at Washington. 



m \ 



Typography by J. S. Ctjshing & Co., Boston, U.S.A. 
Pbesswork by Berwick & Smith, Boston, U.S.A. 



$ 







PREFACE. 



f I ^HIS book is intended for those who are beginning the subject. 
For this reason, special care has been taken to select for 
treatment such compounds as best serve to make clear the 
fundamental principles. General relations as illustrated by special 
cases are discussed rather more fully than is customary in books 
of the same size ; and, on the other hand, the number of com- 
pounds taken up is smaller than usual. The author has endeav- 
ored to avoid dogmatism, and to lead the student, through a 
careful study of the facts, to see for himself the reasons for 
adopting the 'prevalent views in regard to the structure of the 
compounds of carbon. Whenever a new formula is presented, 
the reasons for using it are given so that it may afterward be 
used intelligently. It is believed that the book is adapted to 
the needs of all students of chemistry, whether they intend 
to follow the pure science, or to deal with it in its applica- 
tions to the arts, medicine, etc. It is difficult to see how, 
without some such general introductory study, the technical 
chemist and the student of medicine can comprehend what is 
usually put before them under the heads of "Applied Organic 
Chemistry " and " Medical Chemistry." 

Without some direct contact with the compounds considered, 
it is impossible to get a clear idea regarding them and their 
changes. A course of properly selected experiments, illustrating 
the methods used in preparing the principal classes of com- 
pounds, and the fundamental reactions involved in their trans- 
formations, wonderfully facilitates the study. The attempt has 



IV PREFACE. 

been made to give directions for such a course. More than 
eighty experiments which could be performed in any chemical 
laboratory are described; and it is hoped that the plan may 
meet with approval. The time required to perform a fair pro- 
portion of these experiments is not great; and the results in the 
direction of enlarging the student's knowledge of chemical phe- 
nomena, will, it is firmly believed, furnish a full compensation 
for the time spent. 

The order in which the topics are taken up will be found to 
differ somewhat from that commonly adopted. The object in view 
was, however, not to find a new method, but to find one which 
would bring out as clearly as possible the beauty and simplicity 
of the relations which exist between the different classes of car- 
bon compounds. The reasons for the method used are given in 
the body of the book. 



The experience of the past few years in the use of this book as 
a laboratory-guide for students has revealed a number of imper- 
fections in the descriptions of experiments. The author has now 
gone carefully over the whole book, and has made such corrections 
and additions as seemed desirable. By following the new directions 
conscientiously the student will, it is believed, find no serious diffi- 
culty in getting satisfactory results. The text proper, as well as 
the directions for work, has been thoroughly revised. 



Again this book has been subjected to a thorough revision. The 
chapter on the Carbohydrates has been almost entirely rewritten, 
and the most recent results obtained in the investigation of these 
compounds have been presented. 



CONTENTS, 



CHAPTER I. 
Introduction. 

PAGE. 

Sources of compounds. — Purification of the compounds. — Deter- 
mination of the boiling-point. — Determination of the melting- 
point. — Analysis. — Formula. ■ — Structural formula. — General 
principles of classification of the compounds of carbon ... 1 



CHAPTER II. 

Methane and Ethane. —Homologous Series. 

Methane. — Ethane 20 

CHAPTER in. 

Halogen Derivatives of Methane and Ethane. 

Substitution. — Chloroform. — Iodoform. — Di-chlor- ethanes. — 
Isomerism 26 

CHAPTER IV. 

Oxygen Derivatives of Methane and Ethane. 

Alcohols. — Methyl alcohol. — Ethyl alcohol. — Fermentation. — 
Ethers. — Ethyl ether. — Mixed ethers. — Aldehydes. — For- 
mic aldehyde. — Acetic aldehyde. — Paraldehyde. — Metalde- 
hyde. — Chloral. — Acids. — Formic acid. — Acetic acid. — 
Ethereal salts. — Ketones. — Acetone 34 



VI CONTENTS. 

CHAPTER V. 
Sulphur Derivatives of Methane and Ethane. 

PAGE. 

Mercaptans. — Sulphur ethers. — Sulphouic acids 74 

CHAPTER VI. 

Nitrogen Derivatives of Methane and Ethane. 

Cyanogen. — Hydrocyanic acid. — Cyanides. — Cyanuric acid. — 
Sulpho-cyanic acid. — Cyanides. — Isocyanides or carbamines. 
— Cyanates and isocyanates. — Sulpho-cyanates. — Isosulpho- 
cyanates or mustard oils. — Substituted ammonias. — Hydra- 
zine compounds. — Nitro-compounds. — Nitroso- and isonitro- 
so-compounds . . . . , 79 

CHAPTER VII. 

Derivatives of Methane and Ethane containing Phos- 
phorus, Arsenic, etc. 

Phosphorus compounds. — Arsenic compounds. — Zinc ethyl. — 
Sodium-ethyl. — Retrospect 103 

CHAPTER VIII. 

The Hydrocarbons of the Marsh-Gas Series, or Paraffins. 

Petroleum. — Synthesis of paraffins. — Isomerism among the paraf- 
fins. — Hexanes 108 

CHAPTER IX. 

Oxygen Derivatives of the Higher Members of the 
Paraffin Series. 

Alcohols. — Normal propyl alcohol. — Secondary propyl alcohol. — 
Secondary alcohols. — Butyl alcohols. — Peotyl alcohols. — 
Aldehydes. — Acids. — Eatty acids. — Propionic acid. — Bu- 



CONTENTS. Vll 

PAGE. 

tyric acids. — Valeric acids. — Palmitic acid. — Stearic acid. 

— Soaps. — Polyacid alcohols and polybasic acids. — Di-acid 
alcohols. — Ethylene alcohol or glycol. — Bibasic acids. — 
Oxalic acid. — Malonic acid. — Succinic acids. — Pyrotartaric 
acid. — Tri-acid alcohols. — Glycerin. — Ethereal salts of gly 
cerin. — Fats. — Tri-basic acids. — Tetr-acid alcohols. — Pent- 
acid alcohols. — Hex-acid alcohols 120 

CHAPTER X. 
Mixed Compounds. — Derivatives of the Paraffins. 

Hydroxy-acids. — Carbonic acid. — Glycolic acid. — Lactic acids. 

— Hydroxy-acids, C n H 2n 04. — Glyceric acid. — Hydroxy-acids, 
C n H2n-205. — Tartronic acid. — Malic acid. — Hyclroxy-acids, 
C n H2n-206. — Mesoxalic acid. — Tartaric acid. — Racemic acid. 

— Inactive tartaric acid. — Hydroxy-acids, C n H2 n -407. — Citric 
acid. — Hydroxy-acids, C n H2n-208. — Saccharic acid. — Mucic 
acid 155 

CHAPTER XL 
Carbohydrates. 
Monosaccharides. — Trioses and tetroses. — Glycerose. — Erythrose. 

— Pentoses. — Arabinoses. — Xylose. — Rhamnose. — Hexoses. — 
Glucose. — Fructose. — Mannose. — Galactose. — Polysaccharides 
or complex sugars. — Cane sugar. — Sugar of milk. — Maltose. 

— Polysaccharides not resembling sugars. — Cellulose. — Gun 
cotton. — Paper. — Starch. — Dextrin. — Gums 177 

CHAPTER XII. 
Mixed Compounds containing' Nitrogen. 
Amido-acids. — Amido-formic acid. — Glycocoll. — Sarcosine. — 
Amido-propionic acids. — Leucine. — Amido-sulphonic acids. 

— Taurine. — Cyan-amides. — Guanidiue. — Creatine. — Urea 
or carbamide and derivatives. — Substituted ureas. — Para- 
banic acid. — Oxaluric acicl. — Barbituric acid. — Sulpho urea. 



Vlll CONTENTS. 

PACX 

— Uric acid. — Xanthine. — Theobromine. — Caffeine,, — Guan- 
ine. — Retrospect 192 

CHAPTER XIII. 

Unsaturated Carbon Compounds. — Distinction between 
Saturated and Unsaturated Compounds. 

Ethylene and its derivatives. — Ethylene. — Alcohols, C n H 2n O. 

— Allyl alcohol. — Allyl mustard oil. — Acrolein. — Acids, 
C n H 2n -202. — Acrylic acid. — Crotonic acid. — Oleic acid. — 
Polybasic acids of the ethylene group. — Acids, C 2 H 2 (C0 2 H) 2 . 

— Acids, C 5 H 6 4 . — Aconitic acid. — Acetylene and its deriva- 
tives. — Acetylene. — Propargyl alcohol. — Acids, C n H2n-402. 

— Propiolic acid. — Tetrolic acid. — Sorbic acid. — Leinolei'c 
acid. — Valylene. — Dipropargyl 210 

CHAPTER XIV. 

The Benzene Series of Hydrocarbons. — Aromatic 
Compounds. 

Benzene. — Toluene. — Xylenes. — Ethyl-benzene. — Mesitylene. — 
Pseudocumene. — Cymene 232 

CHAPTER XV. 

Derivatives of the Hydrocarbons, C n H2n-6, of the 
Benzene Series. 

Halogen derivatives of benzene. — Bibrom-benzene. — Halogen 
derivatives of toluene. — Halogen derivatives of the higher 
members of the benzene series. — Nitro compounds of benzene 
and toluene. — Mono-nitro-benzene. — Dinitro-benzene. — Nitro- 
toluenes. — Amido compounds of benzene, etc. — Aniline. — 
Toluidines. — Diazo compounds of benzene. — Sulphonic acids 
of benzene. — Phenols, orhydroxyl derivatives of benzene, etc. 

— Mon-acid phenols. — Phenol. — Tri-nitro-phenol. — Phenyl 
mercaptan. — Cresols. — Thymol. — Di-acid phenols. — Pyro- 



CONTENTS. IX 

PAGE. 

catechin. — Resorcin. — Styphnic acid. — Hydroquinone. — 
Orcin. — Tri-acid phenols. — Pyrogallol. — Alcohols of the 
benzene series. — Benzyl alcohol. — Aldehydes of the benzene 
series. — Oil of bitter almonds. — Cuminic aldehyde. — Acids 
of the benzene series. — Monobasic acids, C n H 2 n-802. — Ben- 
zoic acid. — Substitution products of benzoic acid. — Isatine. 

— Hippuric acid. — Toluic acids. — a-Toluic acid. — Oxindol. 

— Mesitylenic acid. — Hydro-cinnamic acid. — Hydro-carbo- 
styril. — Bibasic acids, C n H 2n -io04. — Phthalic acid. — Iso- 
phthalic acid. — Terephthalic acid. — Hexabasic acid. — Mel- 
litic acid. — Phenol-acids, or Hydroxy-acids of the benzene 
series. — Salicylic acid. — Oxybenzoic acid. — Para-oxybenzoic 
acid. — Anisic acid. — Di-hydroxy-benzoic acids, C 7 H 6 4 . — 
Protocatechuic acid. — Vanillic acid. — Vanillin. — Tri-hy- 
droxy-benzoic acids, C 7 H 6 5 . — Gallic acid. — Tannic acid. — 
Ketones and allied derivatives of the benzene series. — Qui- 
nones. — Pyridine bases. — Pyridine. — Terpenes. — Camphor. 254 

CHAPTER XVI. 

Di-phenyl-methane, Tri-phenyl-methane, Tetra-phenyl- 
methane, and. their Derivatives. 

Tri-phenyl-methane. — Aniline dyes. — Para-rosaniline. — Rosani- 
line. — Phthale'ins. — Phenol-phthale'ins. — Fluorescein. — Eosin. 315 

CHAPTER XVII. 

Hydrocarbons, C n H2n-8, and Derivatives. 

Styrene. — Styryl alcohol. — Cinnamic acid. — Coumarin . . . 325 

CHAPTER XVIII. 

Phenyl-acetylene and Derivatives. 

Phenyl -acetylene. — Phenyl-propiolic acid. — Ortho-nitro-phenyl- 
propiolic acid. — Indigo and allied compounds. — Indigo-blue. 

— Indigo-white 330 



CONTENTS. 



CHAPTER XIX. 



Hydrocarbons containing 1 two Benzene Residues in 
Direct Combination. 

PAGE. 

Diphenyl. — Naphthalene. — Quinoline and analogous compounds. 335 



CHAPTER XX. 

Hydrocarbons containing- two Benzene Residues in 
Indirect Combination. 

Anthracene. — Anthraquinone. — Alizarin. — Purpurin. — Phenan- 
threne 348 



CHAPTER XXI. 

Glucosides. — Alkaloids, etc. 

Aesculin. — Amygdalin. — Tannins. — Helicin. —• Indican. — My- 
ronic acid. — Salicin. — Saponin. — Alkaloids. — Quinine. — 
Cinchonine. — Cocaine. — Nicotine. — Morphine. — Narcotine. 
— Piperine. — Piperidine. — Strychnine 354 



Index . 359 



CHEMISTET 

OF THE 

COMPOUNDS OF CARBON. 



CHAPTER I. 
INTRODUCTION. 

In studying the compounds of carbon, one cannot fail to 
be struck by their large number, and b}~ the ease with which 
the}^ undergo change when subjected to various influences. 
Mainly on account of the large number, though partly on 
account of peculiarities in their chemical conduct, it is custom- 
ary to consider these compounds hy themselves. At first, 
General Chemistry was divided into Inorganic and Organic 
Chemistry, as it was believed that there were fundamental 
differences between the compounds included under the two 
heads. Those compounds which form the mineral portion of 
the earth were treated under the first head, while those which 
were found ready formed in the organs of plants or animals 
were the subject of organic chemistry. It was believed that, 
as the organic compounds are elaborated under the influence of 
the life process, there must be something about them which 
distinguishes them from the inorganic compounds in whose for- 
mation the life process has no part. Gradually, however, this 
idea has been abandoned ; for, one by one, the compounds 
which are found in plants and animals have been made in the 
chemical laboratory, and without the aid of the life process. 
The first instance of the preparation of an organic compound 
by an artificial method was that of urea. This substance 
was obtained b}' Wohler in 1828 from ammonium cyanate. 
When a water solution of the latter is allowed to evaporate, urea 



Z INTRODUCTION. 

is deposited. Up to the time of Wohler's discovery, the 
formation of urea, like that of other organic compounds, was 
thought to be intimately and necessarily connected with life ; 
but it was thus shown that it could be formed without the inter- 
vention of life. Afterward, it was shown that potassium 
cyanide can be made by passing nitrogen over a heated mixture 
of carbon and potassium carbonate ; and, as potassium cyanate 
can be made from the cyanide by oxidation, it follows that 
urea can be made from the elements. Finally, in 1856, Berthe- 
lot succeeded in making potassium formate by passing carbon 
monoxide o?er heated potassium hydroxide ; and in making 
acetylene, a compound, the composition of which is represented 
by the formula C 2 H 2 , by passing electric sparks between elec- 
trodes of carbon in an atmosphere of hydrogen. Since that 
time, every year has witnessed the artificial preparation, by 
purely chemical means, of compounds of carbon which are found 
in the organs of plants and animals. 

It hence appears that the formation of the compounds of 
carbon is not dependent upon the life process ; that they are 
simply chemical compounds governed by the same laws that 
govern other chemical compounds ; and the name, Organic 
Chemistry, signifying, as it does, that the compounds included 
under it are necessarily related to organisms, is misleading. 
Organic chemistry is nothing but the Chemistry of the Com- 
pounds of Carbon. It is not a science independent of inorganic 
chemistry, but is just as much a part of chemistry as the chem- 
istry of the compounds of sodium, or of the compounds of 
silicon, etc. 

The name Chemistry of the Compounds of Carbon has been 
objected to as being too broad. Strictly speaking, this title 
includes the carbonates, and it is customary to treat of these 
widely distributed substances under the head of Inorganic 
Chemistry. Most books on Inorganic Chemistry also deal with 
some of the simpler compounds of carbon, such as the oxides, 
cyanogen, marsh gas, etc. 



SOURCES OF COMPOUNDS. 6 

This objection is of weight only as far as the carbonates 
are concerned, and it does not appear strong enough to make 
the introduction of a new name necessary. It should be men- 
tioned, however, that the name Chemistry of the Hydrocarbons 
and their Derivatives has recently been suggested. The exact 
significance of this name will appear when the compounds with 
which we shall have to deal come up for consideration. 

Sources of compounds. — The compounds of carbon are, 
for the most part, made in the laboratory ; but in preparing 
them we usually start with a few fundamental compounds 
which are formed by natural processes. A large number, such 
as the sugars, starch, cellulose, and the alkaloids, of which 
morphine, quinine, and nicotine are examples, occur ready 
formed in plants, but always mixed with other substances. 
Others, such as urea, uric acid, albumin, etc., occur in animal 
organisms. Petroleum, which has been formed in nature by 
processes, the exact nature of which has not yet been satis- 
factorily explained, contains a large number of compounds con- 
sisting of onl} r carbon and hydrogen ; and these compounds 
serve as the starting-points in the preparation of a large number 
of derivatives. When coal is heated for the purpose of manu- 
facturing illuminating gas, a very complex mixture of liquid 
and solid products is obtained as a by-product, known as coal 
tar. This substance yields some of the most valued compounds 
of carbon. A larger number of the compounds of carbon are 
obtained from this than from any other one source. When 
bones are heated in the. manufacture of bone-black, an oil 
known as bone oil is obtained. Of late, this has proved to 
be the source of a large number of interesting compounds. 
In the preparation of charcoal by heating wood, the liquid pro- 
ducts are sometimes condensed, and they form the source of 
several important compounds, among which may be mentioned 
wood spirits or methyl alcohol, acetone, and pyroligneous or 
acetic acid. 



4 INTRODUCTION. 

Finally, we are dependent upon the process known as fer~ 
mentation for a number of the most important compounds of 
carbon. Fermentation, as will be shown, is a general term, 
signifying any process in which a change in the. composition of 
a body is effected by means of minute animal or vegetable 
organisms. The best known example of fermentation is that 
of sugar, which gives rise to the formation of ordinary alcohol. 
Alcohol in turn serves as the starting-point for the preparation 
of a large number of compounds. 

Purification of the compounds. — Before the natural 
compounds of carbon can be studied chemically, they must, of 
course, be freed from foreign substances ; and before the con- 
stituents of the complex mixtures, petroleum, coal tar, and bone 
oil can be studied, they must be separated and purified. The 
processes of separation and purification are, in many cases, 
extremely difficult. If the substance is a solid, different 
methods may be used according to the nature of the substance. 
Crystallization is more frequently made use of than any other 
process. This is well illustrated, on the large scale, in the 
refining of sugar, which consists, essentially, in dissolving the 
sugar in water, filtering through bone-black, which absorbs 
coloring matter, and then evaporating down to crystallization. 
When two or more substances are found together, they may, in 
many cases, be separated b}' what is called fractional crystalliza* 
tion. This consists in evaporating the solution until, on cool- 
ing, a comparatively small part of the substance is deposited. 
This deposit is filtered off, and the solution further evaporated ; 
when a second deposit is obtained, and so on to the end. The 
successive deposits thus obtained are then recrystallized, each 
separately, until, finally, the deposits are found to be homo- 
geneous. 

The chief solvents used are water, alcohol, ether, benzine, 
and bisulphide of carbon ; alcohol being the most generally 
applicable. 



PURIFICATION OF THE COMPOUNDS. 



In the case of liquids, the process of distillation is used. 
The apparatus commonly used is illustrated in Fig. 1» 




The only part of the apparatus which requires explana- 

known as the distilling tube. 



tion is the tube A. This is 
It is simply a straight glass 



long and 12 to 



tube, about 16 c 
14 mm 'm diameter, to which is 
attached a smaller branch some- 
what inclined downward. The 
object of the tube is to accom- 
modate a thermometer B, which 
is so fixed by means of a cork, 
that it is in the centre of the 
larger tube, and its bulb directly 
opposite the opening of the 
smaller branch. 

For small quantities of liquids, 
the distilling flask is much used. 




Fig. 2. 



This is a long-necked, round 



6 INTRODUCTION. 

flask, with a branch tube fitted directly into the neck, as shown 
in Fig. 2. In this apparatus, the thermometer is fitted into 
the neck of the flask in the same relation to the exit tube as in 
the larger apparatus. 

For the separation of liquids of different boiling-points, the 
process of fractional or partial distillation is much used. When 
a mixture of two or more liquids of different boiling-points is 
boiled, it will be noticed that the boiling-point gradually .-rises 
from that of the lowest boiling substance to that of the highest. 
Thus, ordinary alcohol boils at 78°, and water at 100°. If the 
two be mixed, and the mixture distilled, it will be found that it 
begins to boil at 78°, but that very little passes over at this 
temperature. Gradually, as the distillation proceeds, the tem- 
perature indicated by the thermometer becomes higher and 
higher, until at last 100° is reached, when all distils over. Now 
the distillates obtained at the different temperatures differ from 
each other in composition. Those obtained at the lower tem- 
peratures are richer in alcohol than those obtained at the higher 
temperatures, but none of them contains pure alcohol or pure 
water. In order to separate the two, therefore, we must pro- 
ceed as follows : A number of clean, dry flasks are prepared for 
collecting the distillates. The boiling is begun, and the point 
at which the first drops of the distillate appear in the receiver is 
noted. That which passes over while the mercury rises through 
a certain number of degrees (3, 5, or 10, according to the char- 
acter of the mixture) is collected in the first flask. The receiver 
is then changed, without interruption of the boiling, and that 
which passes over while the mercury rises through another 
interval equal to the first is collected in the second flask. The 
receiver is again changed, and a third distillate collected ; and 
so on, until the liquid has all been distilled over. It has thus 
been separated into a number of fractions, each of which has 
passed over at different temperatures. In the case of alcohol 
and water, for example, we might have collected distillates from 
78° "to 83°, from 83° to 88°, from 88° to 93°, from 93° to 98°, 



PURIFICATION OF THE COMPOUNDS. 7 

from 98° to 100°. Now a clean distilling flask is taken, an& 
into this the first fraction is poured. This is distilled until the 
thermometer marks the upper limit of the original first fraction, 
the new distillate being collected in the flask which contained the 
first fraction. When this upper limit is reached, the boiling is 
stopped. It will be found that there is some of the liquid left 
in the distilling flask. That is to say, assuming that in the first 
distillation the first fraction was collected between 78° and 83°, 
on boiling this fraction the second time it will not all come over 
between these points ; when 83° is reached some will be left in 
the flask. The second fraction is now poured into the distilling 
flask through a funnel tube, and the boiling is again started. 
Of the second fraction, a portion will pass over below the point 
at which it began to boil when first distilled. Collect in the 
proper flask, and continue the boiling until the thermometer 
marks the highest point of the fraction last introduced, changing 
the receiver whenever the indications of the thermometer require 
it. Now stop the boiling, and pour in fraction No. 3, and so 
on until all the fractions have been subjected to a second distil- 
lation. On examining the new fractions, it will be found that 
the liquid tends to accumulate in the neighborhood of certain 
points corresponding to the boiling-points of the constituents of 
the mixture. The distilling flask is now cleaned, and the whole 
process repeated. A further separation is thus effected. By 
continuing the distillation in this way, pure substances can, in 
most cases, eventually be obtained. That the fractions are 
pure can be known b}^ the fact that the boiling-points remain 
constant. In some cases perfect separation cannot be effected 
by means of fractional distillation ; as, for example, in the 
case of alcohol and water. But still it is valuable, even in 
such cases, as it enables us to purify the substances, at least 
partiallv. 

The best examples of distillation carried on on the large scale 
are those of alcohol and petroleum. Probably the best example 
of fractional distillation is that of the light oil obtained from 
coal tar. 



8 INTRODUCTION. 

Experiment 1. Mix equal parts (about half a litre of each) of alco« 
hoi aud water. Distil through four or five times, and notice the 
changes in the quantities obtained in the different fractions. 

Determination of the boiling-point. — In dealing with 
liquids, it often is extremely difficult to tell whether they are 
pure or not. The first and most important physical property 
which is utilized for this purpose is the boiling temperature, 
commonly called the boiling-point. This is determined by 
means of an apparatus, such as is described above as used for 
distilling. The temperature noted on the thermometer when 
the liquid is boiling is the boiling-point. When great accuracy 
is required, the point observed directly must be corrected, in 
consequence of the expansion of the glass and the cooling of 
that part of the column of mercury which is not in the vapor. 
Full directions for making these corrections can be found in 
larger books. A constant boiling-point is characteristic of a 
pure chemical compound. 

Determination of the melting-point. — Just as the boil- 
ing-point is a very characteristic property of liquid bodies, so 
the melting-point is an equally characteristic property of many 
solid bodies. If a substance begins to melt at a certain tem- 
perature, and does not melt completely at that temperature, it 
is, in all probability, impure. By means of the melting-point 
minute quantities of impurities, which might readily escape 
detection by other means, are often found. In dealing with the 
compounds of carbon, determinations of melting-points are very 
frequently made. In general, only those compounds which have 
constant melting-points are to be regarded as pure. The deter- 
mination is made as follows : Small tubes are prepared by 
heating a piece of ordinary soft glass tubing of 4 mm to 5 mm 
diameter, and drawing it out. If the parts are drawn apart 
about 12 cm to 15 cm , two small tubes may be made from the 
narrowed portion by melting together in the middle, and then 
filing off each piece where it begins to grow wider near the 



DETERMINATION OF THE MELTING-POINT. 



9 



large tube. These small tubes must have thin walls, and be 
of such internal diameter that an ordinary pin can be intro- 
duced into them. A small quantity of the substance to be 
tested is placed in one of the tubes, enough to make a minute 
column of about 5 mm in height. The tube containing the 
substance is fastened to a thermometer by means of a small 
rubber band cut from a piece of rubber tubing. The band is 
placed near the upper part of the tube, and the lower part of 
the tube, containing the substance, is placed against the bulb 
of the thermometer. Now a beaker glass of about 100 cc 
capacity is filled with pure paraffin, and the latter melted. 
When it is in liquid condition, the thermometer, with the tube 
and substance, is introduced 
into it, and the heating con- 
tinued with the aid of a 
small flame until the sub- 
stance melts. The instant it 
melts the temperature indi- 
cated by the thermometer 
is noted. This is the melt- 
ing-point required. It is 
necessary, however, to cor- 
rect the observed point in 
the same way as in the case 
of the boiling-point. Some- 
times, instead of paraffin, 
concentrated sulphuric acid 
is used in the bath ; and 
instead of a beaker, a small 
round-bottomed flask. For 
substances which melt below 

80°, the temperature at which ordinary paraffin is liquid, water 
or sulphuric acid should be used. 

Experiment 2. Determine the melting-points of a few substances, 
such as urea and tartaric acid. If they do not melt at definite points, 
recrystallize them until they do. Note the melting-points observed, 




10 INTRODUCTION. 

and see how well they agree with those stated in the book. The 
arrangement of the apparatus above described is shown in Fig. 3. To 
secure a uniform temperature of the bath, it should be geutly stirred 
with a glass rod during the experiment. The mercury of the ther- 
mometer should rise slowly. 

Analysis. — Having purified the compounds, the next step 
is to determine their composition. A comparatively small num- 
ber of the compounds ordinarily met with consist of carbon and 
hydrogen only ; the largest number consist of these two elements 
together with oxygen ; many contain carbon, hydrogen, oxygen, 
and nitrogen. But, in the derivatives of the fundamental com- 
pounds, all other elements may occur. Thus the hydrogen may 
be partly or wholly replaced by chlorine, bromine, or iodine, as 
in the so-called substitution-products ; and any metal may occur 
in the salts of the acids of carbon. The estimation of carbon 
and hydrogen is the principal problem in the analysis of the 
compounds of carbon. This is effected by what is known as 
the combustion process. A known weight of the substance is 
completely oxidized, the carbon being thus converted into car- 
bon dioxide, and the hydrogen into water. These two products 
are collected, the carbon dioxide in a solution of potassium 
hydroxide, the water in calcium chloride, and weighed. From 
the weights of the products the weights of carbon and hydrogen 
are calculated. Ox3'gen, if present, is not estimated directly, 
but by difference, i.e., the weights of carbon and hydrogen found 
are added together, and the sum subtracted from the weight of 
the original substance. The difference represents the weight 
of the oxygen. 

A detailed description of the apparatus and of the method of 
procedure need not be given here, as it can be found in any 
book on analytical chemistry. A brief description, however, 
may not be out of place. The combustion is effected in a hard 
glass tube which is heated by means of a gas furnace con- 
structed for the purpose. Ordinarily, the substance is placed 
in a narrow porcelain or platinum vessel, called a boat, which is 
introduced into the tube with granulated copper oxide. The 



ANALYSIS. 11 

tube is then connected with (1) a u-tube filled with calcium 
chloride ; (2) a set of bulbs containing a solution of potassium 
hydroxide, and constructed so as to secure thorough contact of 
the passing gases with the solution ; aud (3) a small U-tube 
filled with solid potassium hydroxide. After the combustion is 
completed, a current of pure dry oxygen is passed through the 
tube ; and, finally, air is passed until the oxygen is displaced. 
The method at present used was introduced by Liebig. It 
has contributed very greatly to a thorough understanding of 
the compounds of carbon. 

Two methods are in common use for the estimation of nitrogen 
in carbon compounds. The first is known as the absolute method. 
This consists in oxidizing the substance by means of copper 
oxide ; then decomposing, by means of highly-heated metallic 
copper, any oxides of nitrogen which may have been formed, 
and collecting the nitrogen. The volume of the nitrogen thus 
obtained is measured, and its weight easily calculated. The 
chief difficulty in this method consists in removing the gases 
contained in the apparatus before the combustion is made. To 
do this, the simplest way is to use a mercury air-pump. Several 
simple forms of the pump have been devised for this purpose, 
and some of them work admirably. Having exhausted all the 
air, the combustion is made by heating the tube containing the 
substance and copper oxide and a layer of copper foil ; and, 
finally, the gases are exhausted at the end of the operation. 
The only three gases which can be present, assuming that the 
substance contained nothing but carbon, hydrogen, ox} x gen, and 
nitrogen, are carbon dioxide, water vapor, and free nitrogen. 
The water vapor is, of course, condensed, and the carbon dioxide 
is absorbed by passing the gases through a solution of potassium 
hydroxide, leaving the nitrogen thus alone. 

The second method for the estimation of nitrogen consists in 
heating the substance with a mixture of sodium hydroxide and 
quicklime, called soda-lime. The nitrogen is thus converted 
into ammonia, which is collected in a known quantity of dilute 



12 INTRODUCTION. 

hydrochloric or sulphuric acid. After the operation, the amount 
of acid remaining unneutralized is determined by titration ; and 
from this the amount of ammonia formed can be calculated ; 
and from this, in turn, the amount of nitrogen. This method 
is not applicable to all compounds, because the nitrogen of some 
compounds is not converted into ammonia under the circum- 
stances mentioned. 

As regards the estimation of other constituents of carbon 
compounds, it need only be said that in most cases it is neces- 
sary to get rid of the carbon and hydrogen by some oxidizing 
process before the estimation can be made. Thus, in estimating 
sulphur, it is common to fuse the substance with potassium 
nitrate and Irydroxide, when the carbon and hydrogen are 
oxidized, and the sulphur is left in the form of potassium sul- 
phate, and can be estimated in the usual way. 

Formula. — The deduction of the formula of a compound 
from the results of the analysis involves two steps. The first 
is a matter of simple calculation. It is assumed that the 
students who use this book are already familiar with the method 
of calculating the formula from the analytical results ; but an 
example will, nevertheless, be given. Suppose that the analysis 
has shown that the substance contains 52.18 per cent carbon, 
13.04 per cent hydrogen, and 34.78 per cent oxygen. To get 
the atomic proportions, divide the figures representing the per- 
centages of the elements by the corresponding atomic weights. 
We have thus : — 

Per A . Wt Relative 

Centage. ^* vvt ' No. of Atoms. 

C 52.18 -=- 12 = 4.35 - 2 
H 13.04 -T- 1 = 13.04 - 6 
O 34.78 -f- 16 = 2.17 - 1 

That is to say, accepting the atomic weights, 12 for carbon and 
16 for oxygen, the simplest figures representing the number of 
atoms of the three elements in the compound are 2 for carbon, 



FORMULA. 13 

6 for hydrogen, and 1 for oxygen. According to this, the 
simplest formula which can be assigned to a substance giving 
the above results on analysis is C 2 H 6 0. But the formula 
C^^Oa is equally in accordance with the analytical results, and 
we can only decide between the two by determining the molecular 
weight. This, as is known, is done by determining the specific 
gravity of the substance in the form of vapor. This operation 
is of the greatest importance. It is assumed that the student, 
who has already studied the elements of inorganic chemistry, is 
familiar with it, and with the exact connection which exists 
between it and the molecular weights of compounds. A few 
statements in regard to the connection will, however, be made 
here, in order to recall its chief points, and to impress upon the 
mind of the student its fundamental importance. 

Every chemical formula is intended to represent the molecule 
of a compound and the composition of the molecule. Our 
conception of the molecule is based almost exclusively on 
Avogadro's hypothesis, according to which equal volumes of all 
gases contain the same number of molecules. Hence, by com- 
paring equal volumes of bodies in the form of gas or vapor, we 
get figures which bear to each other the same relations as the 
weights of the molecules. The figures called the specific gravi- 
ties express the relations between the weights of equal volumes. 
In the case of gases, air is taken as the standard, and the 
weights of other gases are compared with this standard. Thus, if 
we say that the specific gravity of a gas is 0.918, we mean that 
if we call the weight of any volume of air 1, that of the same 
volume of the other gas measured under the same conditions of 
temperature and pressure is 0.918. If we assign to any com- 
pound a certain molecular weight, the molecular weights of other 
gaseous compounds can be determined without difficulty. We 
must, therefore, first select some substance, the molecule of 
which may be used as the standard. Hydrochloric acid is 
commonly taken, because hydrogen and chlorine unite with 
each other in only one proportion, and there is good evidence 



14 INTRODUCTION. 

in favor of the view that it represents the simplest kind of 
combination, viz., that of one atom of one element with one of 
another. Hydrogen and chlorine are present in the compound 
in the proportion of 1 part of hydrogen to 35.4 parts of chlorine ; 
hence the simplest molecular weight which can be assigned to 
the compound, the atomic weight of hydrogen being 1, is 36.4. 
The molecular weight of this standard molecule is, therefore, 
taken to be 36.4, and we have now simply to compare the 
weights of other gases with that of hydrochloric acid in ordei 
to know their molecular weights. Thus, to illustrate by means 
of the body whose atomic relations we found by analysis to be 
represented by the formulas C 2 H 6 0, C 4 H 12 2 , etc., if this body 
be converted into vapor and its specific gravity determined, it 
might be found to be 1.6. The relation between the molecular 
weight of any body and its specific gravity is expressed by the 
equation 

M = d x 28.88, 

in which M is the molecular weight, and d the specific gravity 
of the substance in the form of gas or vapor. As d is 1.6 in 
the case under consideration, we have 

M (the unknown molecular weight) = 1.6 X 28.88 = 46.2. 

If the formula of the compound is C 2 H 6 0, the molecular weight, 
being the sum of the weights of the constituent atoms, is 

2 X 12 + 6 x 1 + 16 = 46, 

which agrees with the figure deduced from the specific gravity. 
It therefore follows that the formula C 2 H 6 is correct. 

There are some other methods which may be used in deter- 
mining the molecular weight of a compound. Among these 
may be mentioned the analysis of salts. To illustrate this, 
take the case of acetic acid. Analysis shows us that it must be 
represented by one of the formulas CH 2 0, C 2 H 4 2 , C 3 H 6 2 , etc. 
If we make the silver salt, we find that its analysis leads us to 
the formula C 2 H 3 2 Ag, aud not CHOAg, and we hence conclude 
that the molecular formula of acetic acid is C 2 H 4 2 . 



STRUCTURAL FORMULA. 15 

Recently, methods have been introduced that are especially 
applicable to such compounds as cannot be converted into 
vapor. These methods depend upon observations on the 
freezing-points and boiling-points of solutions. 

Structural formula. — The formulas C 2 H 6 2 , C 2 H 4 2 , C 3 H 8 , 

etc., tell us simply the composition of the three compounds repre- 
sented, and tell us also the relative weights of their molecules. In 
studying the chemical conduct of these compounds, their decom- 
positions, and the modes of preparing them, we become familiar 
with many facts which it is desirable to represent by means of 
the formulas. Thus, for example, but one of the four atoms of 
hydrogen represented in the formula of acetic acid, C 2 H 4 2 , can 
be replaced by metals. It plainly differs from the three remain- 
ing atoms, and it is natural to conclude that it is held in the 
molecule in some way differently from the other three. We may, 
therefore, write the formula C 2 H 3 2 .H, which is intended to call 
attention to the difference. By further study of acetic acid, we 
find that that particular hydrogen, which gives to it its acid 
properties, and which, in the above formula, is written by itself, 
is intimately associated with oxygen. It can be removed with 
oxygen by very simple reactions, and the place of both taken 
by one atom of some other element ; as, for example, chlorine. 
Thus, when acetic acid is treated with phosphorus trichloride, 
PC1 3 , it is converted into acetyl chloride, C 2 H 3 0C1, according to 
this equation : — 

3 C 2 H 4 2 + PCI3 = 3 C 2 H 3 0C1 + P0 3 H 3 . 
The result of the action is the direct replacement of one atom 
of hydrogen and one atom of oxygen in acetic acid by one atom 
of chlorine, a fact which certainly points to an intimate connec- 
tion between the hydrogen and oxygen in the acid. Further, 
when acetyl chloride is brought in contact with water, acetic 
acid is regenerated, hydrogen and oxygen from the water enter- 
ing into the place occupied by the chlorine, as represented in 
this equation : — 

C 2 H 3 0C1 + H 2 = C 2 H 4 2 + HC1. 



16 INTRODUCTION. 

From facts of this kind the conclusion is drawn that in acetic 
acid hydrogen and oxygen are connected; or, as it is said, linked 
together ; and this conclusion is represented in chemical lan- 
guage by the formula C 2 H 3 O.OH, which mav serve as a simple 
illustration of what are called structural or constitutional foi- 
mulas. In all compounds the attempt is made, by means of a 
thorough study of their chemical conduct, to trace out the 
connections existing between the constituent atoms. When 
this can be done for all the atoms contained in a molecule, the 
structure or constitution of the molecule or of the compound is 
said to be determined. The structural formulas which have 
been determined by proper methods have proved of much value 
in dealing with chemical reactions, as they enable the chemist 
who understands the language in which they are written to see 
relations which might easily escape his attention without their 
aid. In order to understand them, however, the student must 
have a knowledge of the reactions upon which they are based ; 
and he is warned not to accept airy chemical formula unless he 
can see the reasons for accepting it. He should accustom him- 
self to ask the question, upon what facts is it based? whenever 
a formula is presented for the first time. If he does this con- 
scientiously he will soon be able to use the language intelli- 
gently, and the beaut} T of the relations which exist between the 
large number of compounds of carbon will be revealed to him. 
If he does not, his mind will soon be in a hopeless muddle, 
and what he learns will be of little value to him. For the 
beginner, this piece of advice is of vital importance : Study 
ivith great care the reactions of compounds ; study the methods oj 
malting them, and the decompositions which they undergo. The 
formulas are but the condensed expressions of the conclusions 
which are drawn from the reactions. 

General principle of classification of the compounds 
of carbon. — In considering the elements and compounds in- 
cluded under the head of Inorganic Chemistry, the fundamental 



CLASSIFICATION OF COMPOUNDS OF CARBON. 17 

substances are, of course, the elements. The properties of the 
elements enable us to separate them, for study, into a numbei 
of groups ; as, for example, the chlorine group, including 
bromine, iodine, and fluorine ; the oxygen group, in which 
are included sulphur, selenium, and tellurium. To recall the 
method generally adopted, we may take the chlorine group. 
In studying the members of this group, there is found great 
similarity in their properties. Their hydrogen compounds next 
present themselves, and here the same similarity is met with. 
Then, in turn, the oxygen and the ox3 T gen and hydrogen com- 
pounds are considered, and again the resemblances in properties 
between the corresponding compounds of chlorine, bromine, and 
iodine are met with. We thus have groups of elements, and 
of the derivatives of these elements : as, — 

CIO3H 
Br0 3 H 
IO3H, etc. 

Of course, the chlorine group is quite distinct from the oxygen 
group and from all other groups ; and each member of the 
chlorine group is, at least so far as we know, quite independent 
of the other members. We cannot make a bromine compound 
from a chlorine compound, or a chlorine compound from a 
bromine compound without directly replacing the one element 
by the other. 

Now, when we come to study the compounds of carbon, we 
shall find that the same general principle of classification is 
made use of ; only, in consequence of the peculiarities of the 
compounds, the system can be carried out much more perfectly ; 
the members of the same group can be transformed one into 
the other, and it is also possible to pass from one group to 
another by means of comparatively simple reactions. 

The simplest compounds of carbon are those which contain 
only hydrogen and carbon, or the hydrocarbons. All the other 
compounds may be regarded as derivatives of the hydrocarbons. 



CI 


C1H 


Br 


BrH 


I 


IH 



18 INTRODUCTION. 

To begin with, there are several groups or series of hydrocar. 
bons, which correspond somewhat to the different groups of 
elements. The members of one and the same series of hydro- 
carbons resemble one another more closely thau the members of 
one and the same series of elements. Although we have indica- 
tions of the existence of more than ten series of these hydrocar- 
bons, only three or four of the series are at all well known, and 
of these, but two include more than two or three members which 
will need to be considered in this book. 

Starting with any series of hydrocarbons, several classes of 
derivatives can be obtained by treating the fundamental com- 
pounds with different reagents. The chief classes of these 
derivatives are : (1) those containing halogens ; (2) those con- 
taining oxygen, among which are the acids, alcohols, ethers, etc.; 
(3) those containing sulphur ; and (4) those containing nitro- 
gen. Corresponding to eveiy hydrocarbon, then, we may expect 
to find representatives of these different classes of derivatives. 
But the relations existing between any hydrocarbon and its 
derivatives are the same as those existing between any other 
hydrocarbon and its derivatives. Hence, if we know what 
derivatives one hydrocarbon can yield, we know what deriva- 
tives we may expect to find in the case of every other hydro- 
carbon. The student who, for the first time, undertakes the 
study of carbon chemistry, is very apt to feel overwhelmed by 
the enormous number of compounds described in the book or by 
the lecturer. This large number is really not a serious matter. 
No one is expected to become acquainted with every compound. 
A great many of these need only be referred to for the purpose 
of indicating the extent to which the series to which they belong 
have been developed. In general, the members of any series 
so closely resemble one another, that, if we understand the 
simpler members, we have a fair knowledge of the more com- 
plicated members. 

It is proposed, in this treatise, to consider only the more 
important compounds and the more important reactions, the 



CLASSIFICATION OF COMPOUNDS OF CARBON. 19 

object being rather to give a clear, general notion of the subject, 
than detailed information regarding particular compounds. 
Should the student desire more specific information concerning 
the properties of any of the compounds mentioned, he can 
easily find it in some larger book. It will, however, hardly 
be profitable for him, at the outset, to burden his mind with 
details. He may thereby sacrifice the general view, which it 
is so important that-he should gain as quickly as possible. 

The plan which will be followed is briefly this : Of the first 
series of hydrocarbons two members will be considered. Then 
the derivatives of these two will be taken up. These deriva- 
tives will serve admirably as representatives of the correspond- 
ing derivatives of other hydrocarbons of the same series, and of 
other series. Then* characteristics, and their relations to the 
lryclrocarbons will be dwelt upon, as well as their relations to 
each other. Thus, by a comparatively close study of two hydro- 
carbons and their derivatives, we may acquire a knowledge of 
the principal classes of the compounds of carbon. After these 
typical derivatives have been considered, the entire series of 
hydrocarbons will be taken up briefly, only such facts being- 
dealt with at all fully as are not illustrated by the first two 
members. 

After the first series has been studied in this way, and a clear 
idea of the relations between the various classes has been 
obtained, a second series will be taken up and treated in a 
similar way, and so on. But, as already stated, only a few of 
the series require very much attention at the beginning. The 
first series which will be used for the purpose of illustrating the 
general principles is one of the two most important series, and 
of the only two that need be considered at all fully at present. 



CHAPTER II. 

METHANE AND ETHANE. - HOMOLOGOUS 
SERIES. 

If we were to study all the hydrocarbons known, and were 
then to arrange them in groups according to their properties, 
we should find that a large number of them resemble marsh gas 
in their general conduct. Some of the points of resemblance 
are these : They are very stable, resisting with marked power 
the action of most reagents ; and nothing can be added to them 
directly, — if any change takes place in them, hydrogen is first 
given up. On arranging these substances according to the 
number of carbon atoms contained in them, we have a remark- 
able series, the first six members of which, together with their 
formulas, are included in the subjoined table : — 

Methane (or Marsh Gas) CH 4 . 

Ethane C 2 H 6 . 

Propane C 3 H 8 . 

Butane C 4 H 10 . 

Pentane CsH^. 

Hexane . C 6 H 14 . 

On examining the formulas given, we see that the difference in 
composition between any two consecutive members is represented 
by CH 2 . Thus, adding CH 2 to marsh gas, CH 4 , we get ethane, 
C 2 H 6 ; adding CH 2 to C 2 H 6 , we get C 3 H 8 , and so on, in each 
successive step. Any series of this kind, in which the succes- 
sive members increase in complexity by CH 2 , is called an homol- 
ogous series. 

Just as the members of an homologous series of hydrocarbons 



METHANE AND ETHANE. 21 

differ from one another by CH 2 , or some multiple of it, so 
also the members of any class of derivatives of these hydro- 
carbons differ from each other in the same way, and form 
homologous series. Thus, running parallel to the hydrocarbons 
mentioned above, there are two homologous series of oxygen 
derivatives, as indicated below: — 

CH 4 - CH 4 - CH 2 2 . 
C2H 6 — C 2 H 6 — C 2 H 4 2 . 
C^Hs — C 3 H 8 — C 3 H 6 2 . 
C 4 H 10 — C 4 H 10 O — C 4 H 8 2 . 
C 5 H 12 — CsH^O — C 5 H 10 O 2 . 
CeH 14 — C 6 H 14 — C 6 H 12 2 . 

The relation observed between the members of the homologous 
series mentioned is by no means a peculiarity of the marsh gas 
series of hydrocarbons and of their derivatives, but is observed 
in connection with all other series of hydrocarbons and their 
derivatives. 

Strictly speaking, there is perhaps no analogy for this re- 
markable fact among the elements and their compounds, yet 
facts which suggest analogy are known. Consider, for example, 
the chlorine series. We have 

Chlorine, with the atomic weight, 35.4 
Bromine, " " " 80. 

Iodine, " " " 127. 

As is well known, the difference between the atomic weights of 
chlorine and bromine is approximately equal to the difference 
between those of bromine and iodine. In other words, there is 
a regular increase in complexity as we pass from chlorine to 
iodine. Or, at least, there is a regular increase in the atomic 
weights of these similar elements, just as there is a regular 
increase in the molecular weights of the similar members of an 
homologous series. While, however, a satisfactory hypothesis 



22 METHANE AND ETHANE. 

has been offered to account for the latter fact, and experi- 
mental evidence is strongly in favor of the hypothesis, no satis- 
factory explanation of the former has been offered ; or rather 
no satisfactory experimental evidence has been furnished in 
favor of the various hypotheses which from time to time have 
been put forward to account for the similarity between members 
of the same group of elements. 

The view at present held in regard to the nature of homology 
is founded, primarily, upon the idea that carbon is quadrivalent. 
If carbon is quadrivalent, it of course follows that the com- 
pound, marsh gas, CH 4 , is saturated ; that is, the molecule 
cannot take up anything without losing hydrogen. In order, 
therefore, that we may get a compound containing two atoms 
of carbon in the molecule, some of the hydrogen must first be 
given up. With our present views, we cannot conceive of union 
taking place directly between the molecules CH 4 and CH 4 , but 
we can conceive of union taking place between the molecules 
CH 3 and CH 3 , to form a molecule C 2 H 6 , which in turn is satu- 
rated. Representing graphically what is believed to take 
place, we have, first, marsh gas. which we may represent thus, 
H 
I 
H — C — H. If this loses one atom of hydrogen, we have the 

K I 

unsaturated molecule H — C — , which is capable of uniting with 

H 

another molecule of the same kind to form the more complex 

H H 

I I 
molecule H — C — C — H, or C 2 H 6 , which is believed to express 

I I 
H H 

the relation existing between marsh gas, CH 4 , and ethane, C 2 H 6 , 
or between any two adjoining members of an homologous series. 
The evidence in favor of this view will be presented when the 
reactions are considered by means of which the hydrocar- 
bons are made. The explanation offered, and now generally 



METHANE (MARSH GAS, FIRE DAMP). 23 

accepted, involves the idea that carbon atoms have the power 
of uniting with each other. And, as the explanation for the 
relation between the first and second members is, in principle, 
the same as for the relation between the second and third, the 
third and fourth, etc., it appears that this power of carbon atoms 
to unite with one another is very extensive. It is to the power 
which carbon possesses of forming homologous series, or to the 
power of the atoms of carbon to unite with each other, that we 
owe the large number of compounds of this element. 

Methane (marsh gas, fire damp), CHi. — This hydro- 
carbon is found rising from pools of stagnant water in marshy 
districts. If a bottle is filled with water and inverted with a 
funnel in its neck in such a pool, some of the gas can be col- 
lected by holding the funnel over the bubbles rising from the 
bottom. It is also found in large quantities mixed with air, in 
coal mines, and sometimes issues from the earth, together 
with other gases, in the neighborhood of petroleum wells. 

It can be prepared by passing a mixture of carbon disulphide 
and hydrogen sulphide or water vapor over ignited metals, as 
indicated in the following equations : — 

CS 2 -f 2 H 2 S + 8 Cu = CH 4 + 4 Cu 2 S, 
and CS 2 + 2 H 2 + 6 Cu = CH 4 + 2 Cu 2 S + 2 CuO. 

These methods are of special interest for the reason that they 
indicate the possibility of making marsh gas from the elements ; 
carbon disulphide, hydrogen sulphide, and water all being made 
readily from the elements. 

It is formed, as its occurrence in marshes indicates, by the 
decomposition of organic matter under water. In pure con- 
dition it is made most readily by mixing 2 parts sodium acetate, 
2 parts potassium hydroxide, and 3 parts quicklime, and heat- 
ing the mixture. Writing sodium instead of potassium hydrox- 
ide, the action which takes place is represented thus : — 

NaC 2 H 3 2 + NaOH = CH 4 -f Na 2 C0 3 . 



24 METHANE AND ETHANE. 

It will be shown hereafter that most acids of carbon break up 
in a similar way, yielding a hydrocarbon and a carbonate. 

Properties. Marsh gas is colorless and inodorous. It is 
slightly soluble in water, but not so much so as to prevent its 
collection over water. It burns. Its mixture with air is explo- 
sive. It is this mixture which is the cause of the explosions 
which so frequently take place in coal mines. 

Experiment 3. Make marsh gas from dehydrated sodium acetate, 
potassium hydroxide, and calcium oxide, using the substances in the 
proportion stated on the preceding page. Use lus of sodium acetate. 
Collect the gas over water. Burn some as it escapes from a jet. In 
small quantities it does not readily explode with air. 

Reagents, in general, do not act readily upon marsh gas. 
Chlorine in diffused daylight gradually replaces the hydrogen, 
forming a series of compounds which will be considered under 
the head of the halogen derivatives of methane. The simplest 
of them has the composition represented by the formula CH 3 C1, 
and is known as chlor -methane or methyl chloride. 

Ethane, C 2 H 6 . — Ethane rises from the earth from some of 
the gas wells in the regions in which petroleum occurs. It is 
also found dissolved in crude petroleum. 

It can be made from methane by introducing a halogen and 
making a compound like chlor-methane, CH 3 C1. As the corre- 
sponding iodine derivative is less volatile, it is used. This iodo- 
methane, CH 3 I, is treated with zinc or sodium in some neutral 
medium, as, for example, anhydrous ether. The reaction which 
takes place is represented thus : — 

CH 3 I + CH3I 4- 2 Na = C 2 H 6 + 2 Nal. 

This method of building up more complex from simpler hydro- 
carbons has been used extensively ; and it is well calculated 
to show the relations between the substances formed and the 
simpler ones from which they are made. 

An operation of the kind involved in the above-mentioned 



ETHANE. 25 

preparation of ethane is called a synthesis. The essential feature 
of the synthesis is the formation of a more complex substance from 
simpler ones. Our knowledge of the structure of the compounds 
of carbon is largely dependent upon the use of various methods 
of synthesis. For example, in the case under consideration, the 
synthesis gives us at once a clear view of the relations between 
ethane and methane, and also suggests that homology may be 
due to similar relations between the successive members of the 
series, — a view which is fully confirmed by the synthetical prep- 
aration of the higher members. A similar method of synthesis 
has been used in the preparation of tetrathionic acid from 
sodium thiosulphate. The action is represented thus : — 



Na 2 S 2 8 1 T _ NaS 2 3 „ N y 



Two moL sodium Sodium tetra- 

ttdosulphate. thionate. 



CHAPTER III. 

HALOGEN DERIVATIVES OP METHANE 
AND ETHANE. 

Substitution. — When methane and chlorine are brought 
together in diffused daylight, action takes place gradually ; 
hydrochloric acid gas is given off, and one or more products 
are obtained, according to the length of time the action con- 
tinues. The products have been studied carefully, and four 
have been isolated. The composition of these products is repre- 
sented by the formulas CH 3 C1, CH 2 C1 2 , CHC1 3 , and CC1 4 . We 
see thus that the action of chlorine consists in replacing, step 
by step, the hydrogen of the hydrocarbon. The action is repre- 
sented by the four equations : — 

(1) CH 4 + Cl 2 = CH3CI + HC1; 

(2) CH 3 C1 + Cl 2 = CH 2 C1 2 + HC1 ; 

(3) CH 2 C1 2 + Cl 2 = CHCI3 + HC1 ; 

(4) CHCI3 + Cl 2 = CC1 4 + HC1. 

This replacement of hydrogen by chlorine is an example of 
what is known as substitution. We shall find that most hydro- 
carbons are very susceptible to the influence of the halogens 
and a number of other reagents, such as nitric acid, sulphuric 
acid, etc., and that thus a large number of derivatives can be 
made, differing from the hydrocarbons in that they contain one 
or more halogen atoms or complex groups in the place of the 
same number of Irydrogen atoms. It must be borne in mind 
that the mere fact that chlorine, in acting upon marsh gas, 
replaces an equivalent quantity of hydrogen, does not prove that 



M-IODO-METHANE. 21 

the chlorine in the product occupies the same place that the 
replaced hydrogen did. Nevertheless, a careful study of all 
the facts regarding the products thus formed has led to the 
belief that the substituting atom or residue does occupy the 
same place, or bear the same relation to the carbon atom as 
the hydrogen did. 

The name substitution-products properly includes all products 
made from the hydrocarbons, or from other carbon compounds, 
by the substitution process. The principal ones are those 
formed by the action of the halogens, or the halogen substitution- 
products ; those formed by the action of nitric acid, or the nitro- 
substitution-products ; and those formed by the action of sulphuric 
acid, or the sulphonic acids. The last are, however, not com- 
monly spoken of as substitu ion-products. 

Chlor-methane, methyl chloride, CH 3 C1. 

Brom-methane, methyl bromide, CH 3 Br. 

Iodo-methane, methyl iodide, CH 3 I. 

The chlorine and bromine products can be made by treating 
methane with the corresponding element. They can be most 
easily made by treating methyl alcohol with the corresponding 
hydrogen acids : — 

CH 4 + HC1 = CH3CI + H 2 0. 

Methyl alcohol. Chlor-methane. 

Di-iodo-methane, methylene iodide, CELL. — This sub- 
stance is the principal halogen derivative of methane containing 
two halogen atoms. It is made from iodoform or tri-iodo- 
methane, CHI 3 , by treating with hydriodic acid, the latter 
acting as a reducing agent : — 

CHI3 + HI = CHJ 2 + I 2 . 

As will be seen, this is a case of reverse substitution ; in other 
words, the action is the opposite of that described above as 
substitution. Methylene iodicle is a liquid which boils at 180°. 
and has the specific gravity 3.342. 



28 DERIVATIVES OF METHANE AND ETHANE. 

Chloroform, CHC1 3 . ^ The best known and most exten- 
Bromoform, CHBr 3 . > sively used of these three derivatives 
Iodoform, CHI 3 . _) is chloroform or tri-chlor-methane. It 
is made by treating alcohol or acetone with "bleaching powder." 
The action is deep-seated, involving at least three different 
stages. It will be referred to more fully under the head of 
chloral (which see). Chloroform is a heavy liquid of specific 
gravity 1.526. It has an ethereal odor, and a somewhat sweet 
taste. It is scarcely soluble in water. It boils at 62°. It is 
one of the most valuable anaesthetics, though there is some 
danger attending its use. 

Experiment 4. Mix 550s bleaching powder and ~[\ litres water in 
a 3-litre flask. Add 33s alcohol of sp. gr. 0.834. Heat gently on a water- 
bath until action begins. A mixture of alcohol, water, and chloroform 
will distil over. Add water, and remove the chloroform by means of 
a pipette. Add calcium chloride to the chloroform, and, after standing, 
distil on a water-bath. 

Iodoform, which is used quite extensively in surgery, is made 
by bringing together alcohol, an alkali, and iodine. It is a 
solid substance, soluble in alcohol and ether, but insoluble in 
water. It crystallizes in delicate, six-sided, yellow plates. 
Melting-point, 119°. 

Experiment 5. Dissolve 20s crystallized sodium carbonate in 100s 
water. Pour 10§ alcohol into the solution, and, after heating to 60° 
to 80°, gradually add 10s iodine. The iodoform separates from the 
solution. 

Tetra-chlor-methane, CC1 4 , is made by treating carbon disul- 
phide with chlorine, and by treating chloroform with iodine 
chloride, IC1. 

Equivalence of the hydrogen atoms in methane. Having thus 
seen that the hydrogen atoms of methane can easily be replaced, 
the interesting question suggests itself whether these hydrogen 
atoms all bear the same relation to the carbon atom. We 
accept the conclusion that the carbon atom is quadrivalent, 



IODO-ETHANE. 29 

and that each of the four hydrogen atoms is in combination 

H(l) 
I 

with it, as indicated in the formula (4)H — C — H(2). Do the 

H(8) 

atoms numbered 1, 2, 3, and 4 bear the same relation to the 
carbon or not? If they do not, then, on replacing H (1) by 
chlorine, the product should be different from that obtained by 
replacing H (2), H (3), or H (4) ; or, it should be possible 
to make more than one variety of chlor-methane and of similar 
products. This subject is an extremely difficult one to deal 
with. We can only say that, although chlor-methane has been 
made in several ways, the product obtained is always the 
same one ; and the same is true of all other substitution -pro- 
ducts of methane. Hence, we have no reason ivhatever for 
believing that there are any differences between the hydrogen 
atoms of methane. We therefore conclude that they all bear the 
same relation to the carbon atom. 

This conclusion is of fundamental importance in dealing with 
the higher members of the methane series, and, indeed, in deal- 
ing with all carbon compounds, as will be seen later. 



Chlor-ethane, ethyl chloride, C 2 H 5 C1. 

Brom-ethane, ethyl bromide, C 2 H 5 Br. 

Iodo-ethane, ethyl iodide, C 2 H 5 I. 

These substances are all liquids having pleasant ethereal odors. 
The first boils at 12°, the second at 38.8°, and the third at 72°. 
The}' are most readil} 7 made from alcohol, by treating with the 
corresponding hydrogen acids. In the case of the bromide and 
iodide, it is simpler to treat the alcohol with red phosphorus 
and the halogen. The action is similar to that involved in 
making hydrobromic acid by treating water with red phosphorus 
and bromine. It will be shown that alcohol is a hydroxide, 
in which hydroxyl (OH) is in combination with the group C 2 H 5 , 
called ethyl, as represented in the formula C 2 H 5 .OH. When 



30 



DEEIVAT1VES OF METHANE AND ETHANE. 



bromine is brought in contact with red phosphorus, the tribro- 
mide, PBr 3 , is formed, and this acts upon the alcohol thus : — 

C 2 H 5 .OH Br "| 

C 2 H 5 .OH + Br I P = 3 C 2 H 5 Br + P(OH) 8 . 

C 2 H 5 .OH Br J 

When water is used instead of alcohol, the bromine appears in 
combination with hydrogen as hydrobromic acid. 

Experiment 6. Arrange an apparatus as represented in Fig. 4. 
In the flask place 10s red phosphorus and 60s absolute alcohol. Put 
60s bromine in the glass-stoppered funnel, and, by means of the stop- 




cock, let the bromine enter the flask very slowly, drop by drop. After 
allowing the mixture to stand for two or three hours, gently heat the 
water-bath, and the brom-ethane will distil over. Place the distillate in 
a glass-stoppered cylinder, and shake it first with water to which some 
caustic soda has been added, and then two or three times with water 
alone. Separate the water from the brom-ethane either by means of a 
pipette 1 or a separating funnel. Add two or three pieces of fused 

1 A good pipette for separating two liquids of different specific gravities can be easily 
made as follows: Select a piece of glass tubing about 1.5 to 2 cm internal diameter, and a 



ISOMERISM. 



31 



calcium chloride the size of a small marble, and let stand for a few 
hours. Then pour off into a clean, dry distilling bulb, and distil, noting 
the boiling-point. 

Among the many halogen substitution-products of ethane 
containing more than one halogen atom, only two will be men- 
tioned. These are the two di-c7ilor-et7ianes, both of which are 
represented by the formula C 2 H 4 C1 2 . The existence cf these 
two substances, having the same composition but entirely differ- 
ent properties, affords a good example of What is known as 
isomerism. 

Isomerism. — One of the most striking and interesting facts 
with which we become familiar in studying carbon compounds, 
is the frequent occurrence of two, and often more, substances 
containing the same elements in the same proportions by weight. 
Substances which bear this relation to one another are said to 
be isomeric. 

Isomerism is of two kinds : (1) Substances may have the same 
per centage composition and the same molecular weights. Such 
bodies are said to be metameric. The di : chlor-ethanes, C 2 H 4 C1 2 , 
for example, are metameric. (2) Substances which have the same 
per centage composition but different molecular weights are said 
to be polymeric. Acetylene, C 2 H 2 , benzene, C 6 H 6 , and styrene, 
C 8 H 8 , are polymeric. 

second that will fit snugly into it, so that it can be moved up and down without difficulty. 
Draw out the larger tube, and fit to it a tube of about 6 mm diameter and 16 cm long. 
Then draw out this last tube to a small opening. Close the smaller of the two large tubes 
by melting it together. Finally, put this tube into the largest one, and draw over the two 
a broad piece of thick rubber tubing, which will close the opening between the two, and 
at the same time permit the upward and downward movement of the smaller tube. The 
pipette has the form represented in Fig. 5. 



Fig. 5. 

The dimensions may be varied, but the following will be found convenient: length of 
widest tube about 16 to 20 cm ; total length of inner tube, or piston, about 25 to 30 cm . In- 
stead of drawing the large tube out and fitting the smaller tube to it, the union may be 
made by means of a cork. 



32 DERIVATIVES OF METHANE AND ETHANE. 

The cause of isomerism is undoubtedly to be found in the 
different relations which the parts of isomeric compounds bear 
to each other. Our structural formulas, which show the relations 
between the parts of compounds which have been traced out by 
a study of the chemical conduct of these compounds, give us an 
insight into the causes of isomerism. To illustrate, let us take 
the two di-chlor-ethanes. One of these is made by treating 
ethane, the other by treating ethylene, C 2 H 4 , w T ith chlorine. 
In the first case the action is substitution ; in the second, the 
chlorine is added directly to ethylene, thus, — 

C9H4 -j- Cl 2 — C 2 H 4 C1 2 . 

The product from ethylene is called ethylene chloride; that from 
ethane, ethylidene chloride. It will be shown that ethylene is to 

be represented by the formula | ; that is, that in it two hydro- 

CH 2 

gen atoms are in combination with each of the carbon atoms. 

Now, if chlorine is brought in contact with this substance, we 

should naturally expect each of the carbon atoms to take up one 

atom of chlorine, and thus to become saturated, as represented 

in the equation , — 

CH 2 CI CH 2 C1 
I ' + = I 

CH 2 CI CH 2 C1. 

Chlorine is taken up, and it is believed that the etlrylene 
chloride obtained has the structure represented by the formula 

CH 2 C1 

I , the distinctive feature of which is that each of the chlorine 

CH 2 C1 

atoms is in combination with a different carbon atom. 

We, however, can conceive of another possibility ; viz., that 

the chlorine atoms are both in combination with the same 

CHC1 2 
carbon atom, as represented in the formula | , and we 

CH 3 

should be inclined to the view that this represents the structure 



ISOMERISM. 33 

of ethylidene chloride. Fortunately we have experimental evi- 
dence to support this view. It will be shown that aldehyde 

CHO 
has the formula | . When aldehyde is treated with phos- 

CH 3 

phorus pentachloride, two chlorine atoms take the place of the 

oxj-gen. A product which must be represented by the formula 

CHC1 2 

I is formed, and this is identical with ethylidene chloride. 

CH 3 

Thus it will be seen that the difference between the two iso- 
meric compounds, ethylene chloride and ethylidene chloride, 
depends upon the fact that in the former the two chlorine 
atoms are in combination with different carbon atoms, while 
in the latter both chlorine atoms are in combination with the 
same carbon atom. 

General characteristics of the halogen derivatives of methane 
and ethane. The one characteristic to which it is desirable 
that special attention should be called is the firmness with which 
the halogens are held in the compounds. Chlorine, in combina- 
tion with a metal in the form of a soluble compound, can always 
be removed by addition of silver nitrate. It cannot easily be 
so removed when present in substitution products of the hydro- 
carbons. If silver nitrate be added to a solution of chlor- 
methane, CH 3 C1, no precipitate is formed. On the other hand, 
when chlor-methane is heated with a silver compound, the chlorine 
is removed. Sodium and zinc have the power of extracting the 
chlorine, bromine, etc., from halogen derivatives, and this fact 
is taken advantage of in the synthesis of many hydrocarbons. 
(See "Ethane," p. 24.) 



CHAPTER IV. 

OXYGEN DERIVATIVES OP METHANE 
AND ETHANE. 

There are several classes of oxygen derivatives of the hydro- 
carbons. Among them are the important compounds known as 
alcohols, ethers, aldehydes, and acids. Each of these classes 
will be taken up in turn. 

1. Alcohols. 

Among the most important oxygen derivatives are the alco- 
hols, of which methyl alcohol, or wood spirits, and ethyl alcohol, 
or spirits of wine, are the best known examples. As far as 
composition is concerned, these bodies bear very simple relations 
to the two hydrocarbons, methane and ethane. These rela- 
tions are indicated by the formulas, — 

Hydrocarbons. Alcohols. 

CH 4 CH 4 

C 2 H 6 C 2 H 6 0. 

The molecule of the alcohol differs from that of the correspond- 
ing hydrocarbon by one atom of oxygen. In order to under- 
stand the chemical nature of alcohols, it will be best to study 
with some care the reactions of one ; and we may take for this 
purpose the simplest one of the series, viz., methyl alcohol. 

Methyl alcohol, CH^O. — This alcohol is also known as 
wood spirits. It is found in nature in combination in the oil 
of wintergreen. It is formed, together with many other sub- 
stances, in the dry distillation of wood. It is hence contained 
in crude pyroligneous acid or wood vinegar. Wood is distilled 
in large quantities for various purposes ; chiefly however, for 



METHYL ALCOHOL. 35 

making charcoal. In some charcoal factories the distillate is 
collected and utilized. Wood is distilled also for the purpose 
of making vinegar, or pure acetic acid. 

It is not an easy matter to get pure methyl alcohol from crude 
wood spirits. Fractional distillation alone will not answer ; 
though, if the mixture is distilled for some time, and the impure 
alcohol thus obtained then converted into some crystalline deriv- 
ative, the latter can be purified and then decomposed in such 
a way as to yield the alcohol in pure condition. 

Methyl alcohol is a liquid which boils at 66.7°, and has the 
specific gravity 0.8142 at 0°. It closely resembles ordinary 
alcohol in all its properties. It burns with a non-luminous 
flame. When taken into the system it intoxicates. In concen- 
trated form it is poisonous. It is an excellent solvent for fats, 
oils, resins, etc., and is extensively used for this purpose. 

1. Action of hydrochloric, hydrobromic, and other acids on 
methyl alcohol. The action of a few acids is represented by 
the following equations : — 

CH 4 + HBr = CH 3 Br + H 2 ; 
CH 4 + HC1 = CH 3 C1 + H 2 ; 

CH 4 + HNO3 = CH3NO3 + H 2 ; 

2 CH 4 + H 2 S0 4 = (CH 3 ) 2 S0 4 + 2 H 2 0. 

The action is plainly suggestive of that of metallic hydroxides 
or bases. In each case the acid is neutralized and water is 
formed, just as the acid would be neutralized by potassium 
hydroxide. 

2. Action of phosphorus trichloride. When phosphorus tri- 
chloride acts on methyl alcohol, the products are chlor-me thane 
and phosphorous acid : — 

3 CH 4 + PCI3 = 3 CH3CI + P(OH) 8 . 

Here an atom of oxygen and an atom of hydrogen are together 
replaced by one atom of chlorine, the reaction being like that 
which takes place between water and phosphorus trichloride : — 

3 H 2 + PCI3 = 3 HC1 + P(OH) 3 . 



36 DERIVATIVES OF METHANE AND ETHANE. 

This fact would lead us to suspect that there is some resem- 
blance between the alcohol and water. 

3. Action of potassium and sodium. When potassium is 
brought in contact with pure methyl alcohol, hydrogen is given 
off, and a compound containing potassium is formed : — 

CH 4 + K = CH3KO + H. 

Further treatment of this compound with potassium causes no 
further evolution of hydrogen, so that plainly one of the four 
hydrogen atoms contained in methyl alcohol differs from the 
other three. 

The resemblance between methyl alcohol and metallic hy- 
droxides ; the replacement of hydrogen and oxygen by chlorine ; 
and the resemblance between the alcohol and water ; and, 
finally, the replacement of one, and only one, hydrogen atom 
by potassium, lead to the conclusion that the alcohol contains 
hydrogen and oxygen in combination, and that the characteristic 
reactions are due to the presence of the group called hydroxyl 
(OH) . The analogy between the alcohol, a metallic hydroxide, 
and water, is shown b} T these formulas: alcohol, CH 3 .OH; 
hydroxide, K.OH ; water H.OH. Thus water appears as the 
type of both the hydroxide and the alcohol, and they ma}^ be 
regarded as derived from water by replacing one hydrogen atom 
by the group CH 3 , in the case of the alcohol, and by the metal 
potassium in the case of the hydroxide. Or, on the other hand, 
methyl alcohol may be regarded as marsh gas in which one of 
the hydrogen atoms is replaced by hydroxyl. This is the view 
which is universally held. 

To test the correctness of the view, we may try to make 
methyl alcohol in some way that will show us of what parts it is 
made up. Thus, we may start with marsh gas, and introduce 
a halogen, as bromine. Now, if we bring brom-me thane to- 
gether with a metallic lrydroxide, the bromine and the metal 
may unite, leaving the hydroxyl and the group CH 3 , which may 
unite also, as indicated in the equation 

CH 3 Br + MOH = CH 3 .OH + MBr. 



ETHYL ALCOHOL. 37 

If methyl alcohol could be made in this way, we should have very 
clear proof of the correctness of the view expressed in the formula 
CHg.OH. Methyl alcohol has been made by this reaction ; and 
it is indeed a general reaction for the preparation of alcohols, so 
that the proof that alcohols are hydroxides is conclusive. 

The reactions above considered show that the part of methyl 
alcohol which corresponds to the metal in the hydroxide is the 
group CH 3 . This it is which enters into the acids in place of 
their hydrogen, and this remains unchanged when potassium 
acts upon the alcohol. It has received the name methyl. Hence 
we have the names methyl alcohol, methyl bromide, methyl 
ether, etc. A group which, like methyl, appears in a number 
of compounds is called a radical, or residue. These names are 
intended simply to designate that part of a carbon compound 
which remains unchanged when the compound is subjected to 
various transforming influences. 

The two most characteristic reactions of methyl alcohol are : 
(1) its power to form salt-like, neutral bodies when treated 
with acids ; and (2) its power to form an acid when oxidized. 

The neutral bodies formed with acids correspond to the salts 
of metals, only they contain the radical, or residue, methyl, 
CH3, in the place of metals. They are called compound ethers 
or ethereal salts. 

The acid formed by oxidation has the composition expressed 
by the formula CH 2 2 . It differs from the alcohol by contain- 
ing one atom of oxyg,er more and two atoms of hydrogen less. 
It will be shown that this acid is the first of an important series 
of acids, known as the fatty acids, each of which bears the same 
relation to a hydrocarbon containing the same number of carbon 
atoms that this simplest acid bears to marsh gas. 

Ethyl alcohol, C,H 5 .OH. — This is the best known sub- 
stance belonging to the class of alcohols. It is known also by 
the names spirits of wine and ordinary alcohol. It occurs in 
small quantities widely distributed in nature. 



38 DERIVATIVES OF METHANE AND ETHANE. 

The one method of preparation upon which we are dependent 
for alcohol is the fermentation of sugar. 

Fermentation. — Whenever a plant juice which contains 
sugar is left exposed to the air, it gradually undergoes a change 
by which it loses its sweet taste. Usually the change consists 
in a breaking up of the sugar into carbon dioxide and alcohol. 
The equation 

OgH^Og = 2 C^HgO -f- 2 CO25 

Sugar. Alcohol. 

approximately expresses what takes place in the process which 
is known as alcoholic fermentation. It has been shown that 
fermentation is caused by the presence of small organized 
bodies, either animal or vegetable. These bodies, which are 
known as ferments, are of different kinds, and cause different 
kinds of fermentation with different products. Among the kinds 
of fermentation the following may be specially mentioned : — 

1. Alcoholic or vinous fermentation. This is caused by a 
vegetable ferment which is contained in ordinary yeast. The 
ferment consists of small, round cells arranged in chains. The 
products of its action are alcohol and carbon dioxide. 

2. Lactic acid fermentation. This is due to a vegetable 
ferment which is contained in sour milk. It has the power of 
transforming sugar into lactic acid. 

3. Acetic acid fermentation. This is due to a peculiar vege- 
table ferment which acts upon alcohol, transforming it into 
acetic acid. 

The germs of the various ferments are in the air ; and, when- 
ever they find favorable conditions, they develop and produce 
their characteristic effects. They will not develop in a solution 
of pure sugar. The variety of sugar which is fermentable, and 
which is the one from which alcohol is obtained, is not our 
ordinar}' cane sugar, but one known as grape sugar ; or, more 
commonly, glucose. In order that the ferments may grow, there 



FERMENTATION. 39 

must be present in the solution, besides the sugar, substances 
which contain nitrogen. These, as well as the sugar, are con- 
tained in the juices pressed out from fruits, and hence these 
juices readily undergo fermentation. 

In the manufacture of alcohol a solution containing either 
starch or sugar is first prepared from the residue of wine presses, ' 
or from some kind of grain or potatoes. In case the solution 
contains grape sugar, this undergoes fermentation directly 
when . the ferment is added. If the substance in solution 
is cane sugar, this is first changed by the ferment into grape 
sugar, and the fermentation then takes place as in the first 
case. 

Experiment 7* Dissolve about 150s commercial grape sugar in 1 to 
1J litres of water in a good-sized, flask. Connect the flask by means of 
a bent tube with a cylinder containing clear lime water. Protect the 
latter from the air by means of a tube containing caustic potash. Now 
add to the solution of grape sugar a little brewer's yeast; close the 
connections, and allow to stand. Soon an evolution of gas will begin, 
and, as this passes through the lime water, a precipitate of calcium 
carbonate will be formed. After the action is over, place the flask in 
a water-bath; connect with a condenser, and distil over 100 cc of the 
liquid. Examine this for alcohol. 

A good way to detect alcohol is this : Warm the solution to be 
tested ; add a small piece of iodine and then caustic potash until the 
color is destroyed. On cooling, a yellow crystalline powder of iodo- 
form is deposited. 

To obtain alcohol from fermented liquids, they must be dis- 
tilled. The ordinary alcohol contains water, and a mixture of 
other alcohols called fusel oil. The latter can be removed partly 
by distillation, and the last portions can be got rid of by filter - 
ing through charcoal. The water cannot be removed completely 
hy distillation, though a product containing about 96 per cent 
of alcohol can be obtained in this way. 

Absolute alcohol is ordinary alcohol from which the water has 
been removed to a considerable extent by means of some dehy- 
drating agent, as quicklime, barium oxide, or anhydrous copper 



40 DERIVATIVES OF METHANE AND ETHANE. 

sulphate. By continued treatment with lime the quantity of 
water can be reduced to one-half a per cent, and this small 
quantity can be removed by treatment with metallic sodium. 

Experiment 8. Prepare absolute alcohol from ordinary strong 
alcohol. For this purpose a good-sized flask is one-half to two-thirds 
tilled with quicklime broken into small lumps. The alcohol is poured 
upon the lime, and allowed to stand at least twenty-four hours, when 
it is distilled off on a water-bath. If the alcohol used contains con- 
siderable water, it is necessary to repeat the treatment with lime. 

Pure ethyl alcohol has a peculiar, pleasant odor. It is 
claimed, however, that perfectly anhydrous alcohol has no 
odor. It remains liquid at very low temperatures, but has 
recently been converted into a solid at a temperature of —130.5°. 
It boils at 78.3°. It burns with a non-luminous flame, which 
does not leave a deposit of soot on substances placed in it. It 
can hence be used for heating purposes in chemical labora- 
tories. When mixed with air its vapor explodes when a flame is 
applied. Its effects upon the human system are well known. 
It intoxicates when taken in dilute form, while in large doses it 
is poisonous. It lowers the temperature of the body from 0.5° 
to 2° when taken internally, although the sensation of warmth 
is experienced. 

Alcohol is the principal solvent for substances of organic 
origin. It is hence extensively used in the arts, as in the manu- 
facture of varnishes, perfumes, and tinctures of drugs. 

The many beverages which are in use depend for their effi- 
ciency upon the presence of alcohol in greater or smaller quantity. 
The milder forms of beer contain from 2 to 3 per cent ; light 
wines, such as claret, about 8 per cent ; while whiskey, brandy, 
rum, and other distilled liquors sometimes contain as much as 60 
to 75 per cent. These distilled liquors are nothing but ordinary 
alcohol with water and small quantities of substances obtained 
from the fruit or grain used in their preparation, or obtained by 
standing in barrels made of oak wood. The different flavors 
are due to the small quantities of these substances. 



FERMENTATION. 41 

Chemical conduct of ethyl alcohol. All that was said in regard 
to the chemical conduct of methyl alcohol applies to ethyl 
alcohol. The action of acids, of phosphorus trichloride, of 
the alkali metals, and of oxidizing agents is the same as in the 
case of methyl alcohol, only the products formed contain the 
radical, ethyl, C 2 H 5 , instead of methyl. 

Note for Student. — The student is advised to write the equa- 
tions representing the action of hydrochloric, hydrobromic, and nitric 
acids ; of phosphorus trichloride ; and of potassium, upon ethyl alcohol. 
What is the composition of the acid formed by oxidation of ordinary 
alcohol? 

2. Ethers. 

As has been shown, when an alcohol is treated with potas- 
sium or sodium, compounds are formed having the for- 
mulas 

CH 3 ONa, CH3OK, C 2 H 5 OK, C 2 H 5 ONa. 

If one of these is treated with a mono-halogen derivative of 
a hydrocarbon, as, for example, iodo-methane, CH 3 I, reaction 
takes place thus : — 

CH 3 ONa + CH3I = C 2 H 6 -f Nal. 

The reaction leaves very little room for doubt in regard to 
the structure of the compound C 2 H 6 0. It must be represented 

by the formula CH 3 - O - CH 3 , or ™ 3 > O, or (CH s ) 2 0. 

CH 3 

Comparing it with methyl alcohol, we see that it is obtained 

from the alcohol by replacing the hydrogen of the hydroxyl by 

methyl, CH 3 . Just as the alcohol is analogous to the hydroxide 

KOH, so the new compound is analogous to the oxide K 2 0. 

It is the representative of a class of bodies known as ethers. 

which are analogous to the oxides of the metals. Our ordinary 

ether is the chief representative of the class. 

While the reaction above mentioned serves admirably to show 

the relations between the alcohols and ethers, it is not the one 



42 DERIVATIVES OF METHANE AND ETHANE. 

that is made use of in their preparation. This consists in treat- 
ing the alcohols with sulphuric acid, and distilling. 

Ethyl ether, C 4 H 10 O = (C 2 H 5 ) 2 0. — This is the substance 
commonly known simply as ether, or sulphuric ether. The latter 
name was originally given to it because sulphuric acid is used 
in its manufacture, and plainly not because any sulphur is con- 
tained in it. 

Theoretically, the simplest way to make ether from alcohol 
is to make the sodium compound of alcohol, C 2 H 5 ONa, and to 
heat this with brom- or iodo-ethane thus : — 

C 2 H 5 ONa + C 2 H 5 I = (C 2 H 5 ) 2 + Nal. 

Practically, however, ether can be made much more readily, 
and it is made on the large scale by mixing sulphuric acid and 
alcohol in certain proportions, and then distilling the mixture 
as described below. Two distinct reactions are involved in this 
process. First, when alcohol and sulphuric acid are brought 
together, half the hydrogen of the acid is replaced by ethyl 
thus : — 

C 2 H 5 OH + ** > S0 4 = Cs ^ 5 > S0 4 + H 2 0. 

xi xi 

The product formed is called ethyl- sulphuric acid. 

Experiment 9. "Slowly pour 20 to 30 cc concentrated sulphuric acid 
into about the same volume of alcohol of 80 to 90 per cent. Stir 
thoroughly, and dilute with a litre of water. In an evaporating dish 
add powdered barium carbonate until the liquid is neutral. Filter, 
and examine the clear filtrate for barium. Its presence shows that a 
soluble barium salt has been formed. This is barium ethyl-sulphate, 
Ba(C 2 H 5 SO,) 2 . 

When ethyl-sulphuric acid is heated with alcohol, ether is 
formed, and sulphuric acid is regenerated thus : — 

C 2 H 5 OH + C &* > SO, = ^ 2 H 5 > O -f H 2 S0 4 . 

XX ^2^5 



ETHYL ETHEE. 



43 



The ether thus formed distils over ; and, if alcohol is admitted 
to the sulphuric acid, ethyl-sulphuric acid will again be formed, 
and with excess of alcohol it will yield ether. The actual 
method of procedure is described in 

Experiment 10. Arrange an apparatus as shown in Fig. 6. In 
the flask put a mixture of 200s alcohol, and 360s ordinary concen- 
trated sulphuric acid. It is better to mix them in another vessel, 
and allow the mixture to stand for some time until it is thoroughly 




Fig. 6. 

cooled down ; and then to pour off from any deposited solid as com- 
pletely as possible. Now heat until the thermometer indicates the 
temperature 140°. At this point the mixture boils, and ether begins to 
pass over. As soon as this is noticed, open the stop-cock of the vessel 
A, and let a slow stream of alcohol pass into the distilling flask through 
the tube B, which must reach beneath the surface of the mixture. 
Regulate this stream so that the temperature remains as near 140° as 
possible. In this way the operation can be kept up for a considerable 
time, the alcohol admitted to the flask passing out as ether, and being 
collected together with some alcohol in the receiver. After about a 
half litre to a litre of distillate has been collected, stop the operation. 
The mixture in the distilling flask can be kept in a stoppered bottle 
and used again when needed. Pour the distillate into a glass-stoppered 



44 DERIVATIVES OF METHANE AND ETHANE. 

cylinder, and add water. The ether will rise to the top, forming a 
distinct layer, and can be removed by means of a pipette or separating 
funnel. It should be shaken in this way a few times with water; then 
treated with a little calcium chloride ; and, after standing, poured off 
into a dry flask, aud distilled on a water-bath. 

N.B. Never boil ether over a free flame ; and, in working with it, 
always carefully avoid the neighborhood of flames. In boiling it on a 
water-bath, do not heat the water to boiling. 

Ether is a colorless, mobile liquid of a peculiar odor and 
taste. It boils at 34.9°. (Hence the necessity for the pre- 
cautions mentioned above.) Its specific gravity is 0.736 at 0°. 
(What evidence ■ have you had that it is lighter than water ?) 
It is very inflammable. 

Experiment 11. Put a few cubic centimetres of ether in a small 
evaporating dish, and apply a flame. 

When its vapor is mixed with air, the mixture is extremely 
explosive. Ether is somewhat soluble in water, and water is 
also somewhat, though less, soluble in ether ; so that when the 
two are shaken together the volume of the ether becomes 
smaller, even though every precaution is taken to avoid evapor- 
ation. Ether mixes with alcohol in all proportions. It is a 
good solvent for resins, fats, alkaloids, and many other classes 
of carbon compounds. 

It is an excellent anaesthetic, and is used extensively in this 
capacity. In consequence of its rapid evaporation, it is used 
to produce cold, as in the manufacture of ice. So, also, when 
brought against the skin in the form of spray, the cold produced 
is so great as to cause insensibility. 

Experiment 12. In a thin glass test-tube put 5 CC water. Introduce 
the tube into a small beaker containing some ether. Force air through 
the ether by means of a bellows. The water will be frozen. 

Chemical conduct of ether. If we were dependent upon the 
decompositions and general reactions of ether for our knowledge 
of its structure, we should be left in grave doubt as to the rela- 



MIXED ETHERS. 45 

tions existing between it and alcohol. Its decompositions are 
mostly deep-seated, and not easily explained. Fortunately, as 
we have seen, its synthesis from sodium ethylate, C 2 H 5 ONa, and 
iodo-ethane, C 2 H 5 I, leaves us in no doubt regarding its structure. 
The simplest decompositions are these : — 

Heated with water and a small quantity of sulphuric acid to 
150°, it is converted into alcohol : — 

C 2 H, >0 _ f .H >() = 2C2H50H 

C 2 ±i 5 Jti 

Treated with hydriodic acid at a low temperature, alcohol 
and iodo-ethane are formed : — 

^ 5 >0 -f ^ = C 2 H 5 OH + C 2 H 5 L 

C 2 H 5 1 

Mixed ethers. — Just as ordinary or ethyl alcohol 3-ields 
ethyl ether, so methyl alcohol yields methyl ether, (CH 3 ) 2 0. 
By modifying the method, a mixed ether, methyl-ethyl ether, 

> O, can be obtained. This is formed by treating sodium 



C2H5 



CH 3 

methylate with iodo-ethane, or by treating sodium ethylate with 
iodo-methane : — 

CH 3 ONa + C 2 H 5 I = C ^ 5 > O + Nal ; 
CH 3 

C 2 H 5 ONa + CH 3 I = ^ 2 H 5 >Q + NaT 
CH 3 

It is formed also by distilling methyl alcohol with ethyl-sul- 
phuric acid, or ethyl alcohol with methyl-sulphuric acid : — 

°^ 3 > O + ° 2 !? 5 > S0 4 = ° 2 H 5 > Q + H2S()4 . 
° 2 ^ 5 > O + C ^ 3 > S0 4 = ^ 2 H 5 > O + H 2 S0 4 . 

Methyl ether and methyl- ethyl ether are very similar to ordinary 
ether. 



46 DERIVATIVES OE METHANE AND ETHANE. 

3. Aldehydes. 

It has been stated above that when methyl and ethyl alcohols 
are oxidized, they are converted into acids having the formulas 
CH 2 2 and C 2 H 4 2 , respectively. By proper precautions, prod- 
ucts can be obtained intermediate between the alcohols and 
acids, and differing from them in composition in that they 
contain two atoms of hydrogen less than the corresponding 
alcohols. These products are called aldehydes, from alcohol 
dehydrogenatum, from the fact that they must be regarded as 
alcohols from which hydrogen has been abstracted. The rela- 
tions in composition between the hydrocarbons, alcohols, and 
aldehydes are shown by these formulas : — 



irocarbons 


Alcohols. 


Aldehydes. 


CH 4 


CH 4 


CH 2 


C 2 H 6 


C 2 H 6 


C 2 H 4 


etc. 


etc. 


etc. 



Methyl aldehyde, formic aldehyde, CH 2 0. — This is 
made by gentle oxidation of methyl alcohol, as by passing the 
vapor of the alcohol with air over a heated platinum spiral. It 
is a very volatile liquid, which, up to the present, has not been 
prepared in pure condition. 

In order to*gain a clear insight into the nature of the alde- 
hydes, it will be best to study the best-known representative of 
the class, which is acetic aldehyde. 

Ethyl aldehyde, acetic aldehyde, C^H^O. — The name 
ethyl aldehyde is intended to recall the connection between the 
substance and ethyl alcohol ; while the name acetic aldehyde is 
given to it because, by further oxidation, it is converted into 
acetic acid. The latter is perhaps the better name, as the alde- 
hyde really does not contain ethyl, C 2 H 5 , as is evident from its 
molecular formula. 

Acetic aldehyde is formed whenever alcohol is brought in 



ACETIC ALDEHYDE. 



47 



contact with an oxidizing mixture ; as, for example, potassium 
dichromate and dilute sulphuric acid. 

Experiment 13. Dissolve a little potassium dichromate in water, 
and add sulphuric acid. Now add a few cubic centimetres of alco- 
hol, and notice the odor which is that of aldehyde. Notice, also, 
the change of color of the solution, showing the reduction of the 
chromate. 

As aldehyde is a very volatile liquid, it is difficult to collect it. 
In preparing it, it is therefore better to pass it into some liquid 
which will absorb it, and then afterwards separate it by some 
appropriate method. A good method is that described below. 

Experiment 14. Arrange an apparatus as shown in Fig. 7. Put 
120" granulated potassium dichromate in the flask A, which must have 
a capacity of 1£ to 2 litres. Make a mixture of IGOs concentrated sul- 




Fig. 7. 

phuric acid, 480s water, and 120s alcohol. Cool the mixture down to 
the ordinary temperature, and then pour it slowly through the funnel- 
tube B into the flask, which should stand on a water-bath containing 



48 DERIVATIVES OF METHANE AND ETHANE. 

warm water. The cylinders G and D are about half filled with ordinary 
ether, each one containing about 200 cc ether, and placed in the large 
vessel F, which contains ice water. The condenser should be supplied 
with water of about 30° C. 

Usually, when the alcohol, water, and sulphuric acid are poured upon 
the dichromate, the action begins without application of heat. At times 
it takes place rapidly, so that the liquid should always be added slowly. 
The aldehyde which is thus formed, together with some alcohol and 
water vapor, passes into the condenser-tube, where the greater part of 
the alcohol and water is condensed and returned to the flask, while 
the aldehyde, being much more volatile, passes into the ether and is 
there absorbed. After the action is over, the distilling vessel and con- 
denser are removed, and, at E, connection is made with an apparatus 
furnishing dry ammonia gas. The gas is passed into the cold ethereal 
solution of aldehyde to the point of saturation. A beautifully crystal- 
lized compound of aldehyde and ammonia, known as aldehyde-ammonia, 
is deposited. The ether is poured off, and the crystals placed on filter- 
paper. They gradually undergo change in the air, becoming yellow, 
and acquiring a peculiar odor. If the crystals are placed in a flask and 
treated with dilute sulphuric acid, pure aldehyde passes over, and can 
be condensed by ice-cold water. 

In the process of purification of ordinary alcohol it is filtered 
through charcoal. It is thus partly oxidized to aldehyde ; and, 
when it is afterwards distilled, the first portions which pass 
over contain aldehyde, which was formerly obtained on the 
large scale by repeated distillation of these " first runnings." 

Aldehyde is a colorless liquid, boiling at 21°. It mixes with 
water and alcohol in all proportions. Its odor is marked and 
characteristic. 

From the chemical point of view, the most characteristic prop- 
erty of aldehyde is its power to unite directly with other sub- 
stances. It unites with oxygen to form acetic acid ; with 
hydrogen to form alcohol ; with ammonia to form aldehyde- 
ammonia, C 2 H 4 O.NH 3 ; with hydrocyanic acid to form alde- 
hyde hydrocyanide, C 2 H 4 O.HCN ; with the acid sulphites of 
the alkalies forming compounds represented by the formulas 
C,H 4 O.HKS0 3 and C 2 H 4 O.HNaS0 3 ; and with other substances. 
Indeed, if left to itself, it readily changes into polymeric modi- 



metaldehyde. 49 

fications, uniting with itself to form more complex compounds, 
paraldehyde and metaldehyde. 

Paraldehyde, 6 H 12 O 3 . — This is formed by adding a few 
drops of concentrated sulphuric acid to aldehyde, which causes 
the liquid to become hot. On cooling to 0°, the paraldehyde 
solidifies in crystalline form. It melts at 10.5°. It dissolves 
in eight times its own volume of water, and boils at 124°. When 
distilled with dilute sulphuric acid,, hydrochloric acid, etc., it is 
converted into aldehyde. The specific gravity of its vapor has 
been found to be 4.583. This leads to the molecular weight 
132.4, and consequently to the formula C G H 12 3 . It is called a 
polymeric modification of aldehyde. The cause of the peculiar 
action, and the structure of the product are not known. 

Metaldehyde, C 6 Hi 2 3 . — Metaldehyde is formed in much 
the same way as paraldehyde, only a low temperature (below 
0°) is most favorable to its formation. It crystallizes in needles, 
which are insoluble in water, and but slightly soluble in alcohol, 
chloroform, and ether in the cold, though more readily at a 
slightly elevated temperature. When heated to 120° in a sealed 
tube, it is converted into aldehyde. Determinations by the 
freezing-point method show that the molecular weight of 
freshly prepared metaldehyde is the same as that of paralde- 
hyde. On standing it is converted into paraldehyde and, 
probably, a substance of the formula (C 2 rl 4 0) 4 . Distilled with 
dilute sulphuric acid, etc., metaldehyde is easily converted into 
aldehyde. 

In consequence of the tendency of aldehyde to unite with 
oxygen, it is a strong reducing agent. When added to an 
ammoniacal solution of silver nitrate, metallic silver is deposited 
on the walls of the vessel in the form of a brilliant mirror. 

Experiment 15. To a weak aqueous solution of aldehyde, or of 
aldehyde-ammonia, in a test-tube, add a few drops of ammonia and of 
a solution of silver nitrate. Warm gently ; and, when the deposit on 



50 DERIVATIVES OF METHANE AND ETHANE. 

the walls of the tube begins to appear, stop heating. A brilliant mirroi 
of metallic silver will appear. This method is used in the manufac- 
ture of mirrors. What becomes of the aldehyde? 

Chemical transformations of aldehyde. As aldehyde is pro- 
duced from alcohol by oxidation, so alcohol can be formed 
from aldehyde by reduction : — 

C 2 H 6 + O = C 2 H 4 -f H 2 ; 

C 2 H 4 + H 2 = C 2 H 6 0. 

By oxidation aldehyde is converted into an acid of the formula 
C 2 H 4 2 , which is acetic acid ; and, by reduction, acetic acid is 
converted into aldelryde : — 

C 2 H 4 + O = C 2 HA ; 

C 2 H 4 2 + H 2 = C 2 H 4 + H 2 0. 

Treated with phosphorus pentachloride, aldehyde yields ethyl- 
idene chloride, C 2 H 4 C1 2 (which see). This reaction is of special 
interest and importance, as it helps us to understand the relation 
between aldehyde and alcohol. Alcohol, as has been shown, 
is the Irydroxide of ethyl, C 2 H 5 .OH. When oxidized it loses 
two atoms of hydrogen. Is the hydrogen of the hydroxy 1 
one of the two which are given off? If so, what readjustment 
of the oxygen takes place? Such are the questions which we 
have a right to ask. 

To understand the action of phosphorus pentachloride on 
aldehyde, it will be necessary to consider briefly the action of 
this reagent in general upon compounds containing oxygen. 
When it is brought in contact with water, the first change is 
represented by the equation 

H,0 + PC1 5 = POCI3 + 2 HC1. 

Next, the oxi chloride, POCl 3 , is acted upon thus : — 

3 H 2 + POCl 3 = PO(OH) 3 + 3 HC1. 

Or, expressing both changes in one equation, we have : — 

4 H 2 + PC1 5 = PO(OH) 3 -f- 5 HC1. 



ALDEHYDE. 51 

The phosphorus pentachloride gives up its chlorine and takes 
up oxj'gen, or oxygen and hydrogen, in its place. This is the 
general tendency of the chlorides of phosphorus. 

Now, when a chloride of phosphorus is brought together with 
an alcohol, the oxygen is replaced by chlorine, two atoms of 
the latter for one of the former, thus : — 

C 2 H 5 .OH + PC1 5 = C 2 H 5 C1.C1H + POCl 3 . 

But as hydroxyl, — O — H, is univalent, its place cannot be 
taken by two atoms of chlorine and one of hydrogen, and the 
two chlorine atoms have not the power of linking the hydrogen 
to the ethyl. Hydrochloric acid is given off, and a compound is 
formed, which may be regarded as alcohol in which one chlorine 
atom takes the place of the hydroxyl. This is the kind of 
action which takes place whenever a chloride of phosphorus acts 
upon a compound containing hydroxyl ; and we hence make use 
of the reaction for determining whether hydroxyl is or is not 
present in a compound. 

When aldehyde is treated with phosphorus pentachloride, the 
action is entirely different from that just described. Instead of 
a hydrogen and an oxygen atom being replaced by one chlo- 
rine, the oxygen atom alone is replaced by two chlorine atoms : — 

C 2 H 4 + PC1 5 = C 2 H 4 C1 2 + POCI3. 

If the explanation above offered of the action of phosphorus 
pentachloride on alcohol is correct, it follows that aldehyde is 
not a hydroxyl compound. We can readily understand why the 
oxygen atom should be replaced by two chlorine atoms, if it 
is in combination only with carbon as in carbon monoxide, CO. 
There is an essential difference between this kind of combina- 
tion and that which we have in hydroxyl as C — O — H. In 
the latter condition the oxygen serves to connect carbon with 
hydrogen ; in the former it is in combination only with the 
carbon, and, presumably, the force which holds it can also hold 
two atoms of chlorine or of any other univalent element with 



52 DERIVATIVES OF METHANE AND ETHANE. 

which it can unite. So that, if oxygen is in a compound in 
the carbon monoxide condition, we should expect it to be re- 
placed by two atoms of chlorine when the compound is treated 
with phosphorus pentachloride. Let E.CO represent any such 
compound ; then we should have : — 

RCO + PC1 5 = R.CC1 2 + POCI3 ; 

while, when oxygen is present in the hydroxyl condition, we 
have : — 

R.C - O - H + PC1 5 = R.CC1 4- POCI3 + HC1. 

Just as the latter reaction is used to detect the presence of 
hydroxyl oxygen, so the former is used to detect oxygen in the 
other condition, which is commonly known as the carbonyl con- 
dition. 

In terms of the valence hypothesis, it is said that in the 
hydroxyl compounds oxygen is in combination with carbon with 
one of its affinities^ and with hydrogen with the other, while in 
the carbonyl compounds it is in combination with carbon with 
both its affinities as represented thus, C= O. 

According to the above reasoning aldehyde is a carbonyl 
compound, or it contains the group CO. The simplest alde- 
hyde must therefore be represented by the formula H 2 C = O. 

O 
II 
Its homologue, acetic aldehyde, is CH 3 .C — H. The peculiar prop- 
erties of aldehyde are believed to be due to the presence of this 


li ' 
group, C — H, which is called the aldehyde group. We do not 

"know that the double line in the formula conveys a correct idea 
in regard to the relation between the carbon and oxygen. All 
that we know is that these two elements do occur in two differ- 
ent relations to each other, and the formulas C — O — H and 
C = O recall these relations. They are expressions of facts 
established by experiment. Our notions in regard to these 
relations are largely dependent upon the reactions with the 
chlorides of phosphorus referred to above. 



CHLORAL. 53 

Chloral, trichloraldehyde, CCl 3 .CHO. — When chlorine 
acts directly upon aldehyde, complicated reactions take place 
which need not be considered here. If, however, water and 
calcium carbonate are present, substitution takes place, and 
tr id dor aldehyde is formed. When alcohol is treated with 
chloriue, a double action takes place : 1st. The alcohol is 
changed to aldehyde thus : — 

CH 3 .CH 2 OH + Cl 2 = CH3.COH -f 2 HC1. 

Then the chlorine acts upon the aldehyde, replacing the three 
hydrogens of the metlryl, forming trichloraldehyde : — 

CH3.COH + 6 CI = CCI3.COH + 3 HC1. 

In reality the aldehyde first formed acts upon the alcohol, 
forming an intermediate product which is acted upon by the 
chlorine. The chlorine product thus formed breaks up, forming 
chloral. The essential features of the reaction, however, are 
stated in the above equations. Trichloraldehyde is the sub- 
stance commonly known as chloral. It is simply the tri-chlo- 
rine substitution product of aldehyde. It has all the general 
properties of aldehyde, and the conclusion is therefore justified 

O 

II 
that it contains the aldehyde group — CH. 

Chloral is a colorless liquid, which boils at 94°, and has the 

specific gravity 1.5. 

Note for Student. — Give the formulas of compounds formed 
when chloral is brought together with ammonia, hydrocyanic acid, and 
the acid sulphites of the alkalies. What is the formula of the acid 
formed by its oxidation? The answer is given in the statement that 
the general chemical conduct of chloral is the same as that of aldehyde. 

When chloral and water are brought together, they unite to 
form a crystallized compound, chloral hydrate, C 2 HC1 3 + H 2 0, 
which is easily soluble in water, and crystallizes from the solu 
tion in beautiful, colorless, monoclinic prisms. It melts at 46°. 



54 DERIVATIVES OF METHANE AND ETHANE. 

Taken internally in doses of from 1.5 to 5 g , it produces sleep. 
In larger doses it acts as an anaesthetic. 

When treated with an alkali, chloral and chloral hydrate 
break up, yielding chloroform and formic acid : — 

CCI3.COH + KOH = CHCI3 + KCH0 2 . 

Chloral. Chloroform. Potassium 

formate. 

This reaction, taken together with those which give chloral 
from alcohol, enables us to understand the reaction which is 
used in making chloroform and iodoform. 

Note for Student. — How is chloroform made? How is the method 
explained? Answer the same questions for iodoform. The bleaching 
powder used in preparing chloroform furnishes chlorine. Is an alkali 
present? 

4. Acids. 

When methyl and ethyl alcohols are oxidized, they are con- 
verted first into aldehydes, and then the aldehydes take up 
oxygen and are converted into acids. The relations in compo- 
sition between the hydrocarbons, alcohols, aldehydes, and acids 
are shown in the subjoined table : — 



drocarbons. 


Alcohols. 


Aldehydes. 


Acids. 


CH 4 


CH 4 


CH 2 


CH 2 2 


C 2 H 6 


C 2 H 6 


C 2 H 4 


C 2 H 4 2 


etc. 


etc. 


etc. 


etc. 



The two acids whose formulas are here given are the well- 
known substances, formic and acetic acids. 

Formic acid, 0H 2 O 2 . — This acid occurs in nature in red 
ants, in stinging nettles, in the shoots of some of the varieties 
of pine, and elsewhere. 

It can be prepared by distilling red ants, but is best prepared 
by heating oxalic acid with glycerin. Oxalic acid has the 



FORMIC ACID. 55 

composition represented by the formula C 2 H 2 4 . When heated 
in glycerin, the effect is to break it up into carbon dioxide and 
formic acid : — 

C 2 HA = C0 2 -f- CH 2 2 . 

The formic acid distils over, and can be condeused. 

Experiment 16. Into a flask of 500 to 600 cc capacity put 200 to 
300 cc anhydrous glycerin, and then add 30 to 40s crystallized oxalic 
acid. Connect the flask with a condenser, and insert a thermometer 
through the cork so that the bulb is below the surface of the glycerin. 
Heat gently. At 75° to 90°, carbon dioxide is evolved. Raise the tem- 
perature gradually to 112 c -115°. When formic acid no longer distils 
over, add another portion of oxalic acid, and heat again. This opera- 
tion may be repeated a number of times without renewing the glycerin; 
but, when about 100s of oxalic acid have been decomposed, enough 
formic acid for the purpose will have been formed, and collected in 
the receiver. Dilute the distillate to about half a litre, and, while 
gently warming it in an evaporating dish, add freshly precipitated and 
washed copper oxide in small quantities until no more is dissolved. 
Then filter, and evaporate the solution to crystallization. The beauti- 
fully crystallized salt thus obtained is copper formate. 

The formation of formic acid by oxidation of methyl alcohol, 
and by treatment of chloral with an alkali, has alread}' been 
mentioned. The following methods are of special interest : — 

(1) By the action of carbon monoxide upon potassium hy- 
droxide : — 

CO + KOH = H.C0 2 K. 

This method can be used for the preparation of formic acid on 
the large scale. Soda-lime acts as well as potassium hydroxide. 

(2) By the action of metallic potassium upon moist carbon 
dioxide (carbonic acid) : — 

2 C0 2 + K 2 + H 2 = HC0 2 K + HC0 3 K, 
or 2 C0 3 H 2 + K, = HC0 2 K + HC0 3 K + H 2 C. 



56 DERIVATIVES OF METHANE AND ETHANE. 

(3) By treatment of a solution of ammonium carbonate with 
sodium amalgam : — 

C0 3 (NH,) 2 +2H = HC0 2 (NH 4 ) + H 2 + NH 3 , 
and HC0 2 (NH 4 ) + NaOH = HC0 2 Na + NH 3 + H 2 0. 

According to these last two methods formic acid appears as a 
reduction product of carbonic acid formed by the abstraction of 
one atom of ox} T gen : — 

H 2 C0 3 = H 2 C0 2 + 0. 

It is extremely important to bear this fact in mind, as it is of 
great assistance in enabling us to understand the relation exist- 
ing between the two acids, and between them and all other acids 
of carbon. It will be shown that all the acids of carbon may 
be regarded as derivatives of either formic acid or carbonic 
acid. 

(4) When hydrocyanic acid is left in the presence of an acid 
or an alkali, it breaks up, forming ammonia and formic acid. 
The reaction may be represented thus : — 

HCN + 2 H 2 = H 2 C0 2 + NH 3 . 

Of course, if an acid is present, the ammonium salt of the acid is 
formed ; and, if an alkali is present, the formate of this alkali is 
formed. A reaction similar to this is used very extensively in the 
preparation of the acids of carbon, as will be shown. 

Anhydrous formic acid can be made by dehydrating either 
the copper or lead salt, and passing dry hydrogen sulphide over 
the salt placed in a heated tube. The acid distils over, aud can 
be obtained perfectly pure by placing a little of the anhydrous 
salt in it and redistilling. 

It is a colorless liquid which boils at 99°. It has a pene- 
trating odor. Dropped on the skin, it causes extreme pain and 
produces blisters. Its specific gravity at 0° is 1.22. When 
cooled down it solidifies to a mass of crystals which melt at 8.6°. 



ACETIC ACID. 57 

Concentrated sulphuric acid decomposes it into carbon mon- 
oxide and water : — 

H 2 C0 2 = CO + H 2 0. 

It is easily oxidized to carbonic acid. Hence it acts as a 
reducing agent. Heated with the oxides of mercury or silver, 
they are reduced to the metallic condition : — 

HgO + H 2 C0 2 = Hg + H 2 + C0 2 . 

Like other acids, formic acid yields a large number of salts with 
bases, and ethereal salts or compound ethers with the alcohols. 
These derivatives need not be considered here. The salts are 
all soluble in water, and some of them, as the lead, copper, and 
barium salts, crystallize very well. Some of the compound 
ethers will be mentioned when these substances are considered 
as a class. 

Acetic acid, C 2 H 4 2 . — The two methods by which acetic 
acid is exclusively made are, — 

(1) By the oxidation of alcohol ; and 

(2) By the distillation of wood. 

When pure alcohol is exposed to the air it undergoes no 
change. If, however, some platinum black is placed in it, 
oxidation takes place and acetic acid is formed. So also if 
fermented liquors which contain nitrogenous substances are 
exposed to the air, oxidation takes place, and the liquor becomes 
sour in consequence of the formation of acetic acid. A great 
deal of acetic acid is made b} T exposing poor wine to the action 
of the air. The product is known as wine vinegar. The for- 
mation of vinegar has been shown to be due to the presence of 
a microscopic organism (Mycoderma aceti) commonly known as 
" mother-of- vinegar." This serves in some way to convey the 
oxygen from the air to the alcohol. The " quick- vinegar 
process," much used in the manufacture of vinegar, consists in 
allowing weak spirits of wine to pass slowly through barrels 



58 DERIVATIVES OF METHANE AND ETHANE. 

filled with beech shavings which have become covered with 
Mycoderma aceti. The presence of the organism is secured by 
first pouring strong vinegar into the barrels, and allowing it to 
stand for one or two days in contact with the shavings. 

When wood is distilled, a very complex mixture passes over, 
one of the constituents being acetic acid. By keeping the tem- 
perature down comparatively low, the amount of acetic acid 
obtained is increased. The distillate is neutralized with soda 
ash, and the solution of crude sodium acetate thus obtained 
evaporated to dryness. It is then treated with sulphuric acid, 
and distilled, when acetic acid passes over. 

Besides the two methods mentioned, there are two others 
which may be used for making acetic acid. One of them is a 
modification of a method referred to under formic acid, and, 
from the scientific point of view, both are of great interest. 
They are, — 

(1) By treating carbon dioxide with a compound known 
as sodium-methyl, which may be regarded as marsh gas, in 
which one hydrogen is replaced by sodium as shown in the 
formula CH 3 Na. 

C0 2 + CH 3 Na = CH 3 .C0 2 Na. 

(2) By treating methyl cyanide, CH 3 CN, with an acid or an 
alkali : — 

CH 3 CN + 2 H 2 - CH 3 .C0 2 H + NH 3 . 

This reaction is analogous to that involved in the formation 
of formic acid from hydrocyanic acid (see p. 56). 

Whether the acid is made from alcohol or from wood, it must 
be purified. For this purpose it is passed through charcoal and 
distilled. It still contains water, from which it cannot be 
completely separated by distillation. When cooled down to a 
sufficiently low temperature it solidifies, and the water can 
then partly be poured off. By repeating the freezing, and 
distilling a few times, perfectly pure, anhydrous acetic acid 
can be obtained. 



ACETTC ACID. 59 

Experiment 17. Make pure acetic acid from the commercial sub- 
stance. First distil iu fractions until a portion is obtained that boils 
between 110° and 119°. Put the vessel containing this in ice. The 
liquid will solidify almost completely. Pour off the little liquid which 
remains, and distil. 

Acetic acid is a clear, colorless liquid, which boils at 119°. 
It has a very penetrating, pleasant, acid odor, and a sharp acid 
taste. Tlie pure substance acts upon the shin like formic acid, 
causing pain and raising blisters. It solidifies when cooled down, 
and the crystals melt at 16.7°. The pure acid which is solid at 
temperatures below 16° is known as glacial acetic acid. Its speci- 
fic gravity is 1.08 at 0°. It mixes with water in all proportions. 

Acetic acid is extensively used, chiefly in the dilute, impure 
form known as vinegar. Formic acid would answer perhaps as 
well. It is used in calico printing in the form of iron and alu- 
minium salts. With iron it gives hydrogen, which is needed in 
the manufacture of certain compounds used in making dyes, as, 
for example, aniline. It is an excellent solvent for man} 7 
organic substances, and is therefore frequently used in sci- 
entific researches. 

Derivatives of acetic acid. Acetic acid yields a very large 
number of derivatives. They may be considered briefly under 
two heads : (1) Those which are formed in consequence of the 
acid properties and which necessitate a loss of the acid proper- 
ties, as the salts, ethereal salts, etc. ; and (2) those in which 
the acid properties remain unchanged. 

Salts of acetic acid. The acetates of the alkalies were the 
first compounds of carbon ever prepared. The potassium and 
sodium salts are used in the chemical laboratory- Both crystal- 
lize, the sodium salt particularly well and easily. 

Lead acetate, (CsH^Oo^Pb. This salt, which is commonly 
known as sugar of lead, is made on the large scale by dissolv- 
ing lead oxide in acetic acid. It crystallizes well, and is solu- 
ble in 1.5 parts of water at ordinary temperatures. Commer- 
cial sugar of lead frequently contains an excess of lead oxide iu 



60 DERIVATIVES OF METHANE AND ETHANE. 

the form of basic salts. A solution of such a mixture becomes 
turbid when allowed to stand in the air, or gives a precipitate 
when dissolved in ordinary spring water, in consequence of the 
formation of lead carbonate. 

Copper acetate, (C 2 H 3 2 ) 2 Cu. This salt can be made by 
dissolving copper hydroxide or carbonate in acetic acid. It 
crystallizes in dark-blue, transparent prisms. A basic acetate, 
formed b} T the action of acetic acid on copper in the air, is 
known as verdigris. 

Copper aceto-arsenite, 3 CuAs 2 4 + (C 2 H 3 2 )2Cu. This double 
salt is formed by boiling verdigris and arsenic trioxide together 
in water. It has a fine bright-green color, and is used as a 
coloring matter. It is the chief constituent of emerald green, 
or Schweinfurt's green. 

Iron forms two distinct salts with acetic acid, the ferrous 
salt, (C 2 H 3 2 ) 2 Fe -f 4 H 2 0, and the ferric salt, (C 2 H 3 2 } 6 Fe 2 . 
The latter is formed when sodium acetate is added to an acidi- 
fied solution of a ferric salt. At first the solution becomes 
deep-red in color ; but, on boiling, all the iron is precipitated 
as hydroxide. Hence this salt is used for the purpose of sepa- 
rating iron from manganese in analytical operations. 

Experiment 18. To a dilute solution of ferric chloride, contained 
in a small flask, add a little sulphuric acid and a solution of sodium 
acetate. Boil the red solution, and ferric hydroxide is precipitated,, 
leaving the solution colorless. Filter, and examine the filtrate for iron. 

The ethereal salts will be mentioned briefly when this class 
of compounds is considered. The principal one is ethyl acetate 
or acetic ether, which is formed from acetic acid and ordinary 
alcohol. When a mixture of these two substances is treated 
with sulphuric acid, the ether is formed and can be recognized 
by its pleasant odor. This fact is taken advantage of for the 
detection of acetic acid. 

Experiment 19. To a mixture of about equal parts of acetic acid 
and alcohol, in a test-tube, acid a little concentrated sulphuric acid, and 
notice the odor. It is that of ethvl acetate o; acetic ether. 



ACETYL CHLORIDE, ETC. 61 

Acetic anhydride or acetyl oxide, C 4 H 6 3 . — This sub- 
stance, which bears to acetic acid the relation of an anhydride, 
is made by abstracting water from the acid. 

2 C 2 H 4 2 = C 4 H 6 3 + H 2 0. 

Like other acids, acetic acid contains lrydroxyl, as will be 
shown below. We may hence represent the acid thus : 
CoHoO.OH. The part C 2 H 3 is known as acetjd. Now when 
water is abstracted from the acid, the change takes place as rep- 
resented in this equation : — 

c 2 h 3 o.oh| _ c^cn 

C 2 H 3 O.OH j ~ C 2 H 3 ) + 2 

Hence, according to this, acetic anhydride appears as the oxide 
of acetyl, while the acid itself is the hydroxide. 

Acetic anhydride is a colorless liquid which boils at 138°. 
With water it gives acetic acido 

Acetyl chloride, C 2 H 3 OCl. -\ Just as alcohol, when 
Acetyl bromide, C 2 H 3 OBr. j- treated with phosphorus tri- 
Acetyl iodide, C 2 H 3 OI. 3 chloride, yields a chloride of 
ethyl, so acetic acid, when treated with the same reagent, yields 
acetyl chloride. The character of the reaction is the same in 
both cases. It consists in the replacement of hydroxyl by 
chlorine. 

3 C 2 H 3 O.OH + PC1 3 = 3 C 2 H 3 0C1 + P(OH) 8 . 

Acetyl chloride. 

Experiment 20. Arrange a dry distilling flask, with condenser and 
dry receiver, under a hood or out of doors. Bring together 9 parts 
(say 1808) strong acetic acid and 6 parts (say 120e) phosphorus tri- 
chloride. Slightly heat the mixture on the water-bath, when acetyl 
chloride will distil over. Collect in a dry bottle. 

Acetyl chloride is a colorless liquid which boils at 55°. 
Water acts upon it very readily, acetic and hydrochloric acids 
being formed : — 

C 2 H 3 0C1 + H 2 = C 2 H 3 O.OH + HC1. 



62 DERIVATIVES OF METHANE AND ETHANE. 

Iii this case the chlorine is replaced by hydroxyl. As the sub- 
stance is volatile, it fumes in contact with the air in consequence 
of the formation of hydrochloric acid. It must be kept in 
tightly-stoppered bottles. In handling it, care must be taken 
not to bring it near the nose, as its odor is very suffocating, and 
it attacks the mucous membranes of the eyes and nose, produc- 
ing coughing and other bad results. 

Acetyl chloride is a valuable reagent much used in the exam- 
ination of compounds of carbon. Its value depends upon its 
action towards alcohols. When it is brought together with an 
alcohol, as, for example, methyl alcohol, hydrochloric acid is 
evolved, and the acetyl group takes the place of the hydrogen 
of the alcoholic hydroxyl : — 

CH 3 .OH + C 2 H 3 0C1 = CH 3 .O.C 2 H 3 + HC1. 

The product is an ethereal salt, methyl acetate. This kind of 
action takes place whenever an alcohol is treated with acetyl 
chloride. Hence if, on treating a substance with acetyl chloride, 
its composition is changed, showing that hydrogen is replaced by 
acetyl, we are justified in concluding that the substance contains 
alcoholic hydroxyl. The bromide and iodide resemble the 
chloride ver3' closely. 

Experiment 21. Treat a few cubic centimetres of absolute alcohoi 
with acetyl chloride. Notice the evolution of hydrochloric acid and 
the odor of ethyl acetate. 

Substitution-products of acetic acid. These bear the same 
relation to acetic acid that the substitution-products of marsh 
gas bear to marsh gas. They are formed by the simple sub- 
stitution of a halogen, etc., for hydrogen. Only three of the 
four hydrogen atoms of acetic acid are capable of direct 
replacement. The fourth is the one to which the acid prop- 
erties are due. Hence the substitution-products are acid. The 
best known of these products are the chlor-acetic acids which 
are made by treating the acid with chlorine. They are 



RELATIONS BETWEEN COMPOUNDS OF CARBON. 63 

mono -chlor- acetic, di-clilor- acetic, and tri- chlor- acetic acids. 
Their formation is represented by the following equations : — 

C 2 H 3 O.OH + Cl 2 = C 2 H 2 C10.0H + HC1 ; 
C 2 H 2 C10.0H + Cl 2 = C 2 HCl 2 O.OH + HC1; 
C 2 HCl 2 O.OH + Cl 2 = C 2 CLO.OH + HC1. 

When treated with nascent hydrogen they are converted 
back into acetic acid. They yield salts, ethereal salts, anhy- 
drides, etc., just the same as acetic acid itself. 

Theory in regard to the relations between the acids, alcohols, 
aldehydes, and hydrocarbons. The reactions and methods of 
formation of acetic acid enable us to form a clear conception in 
regard to the relation of its constituents. In the first place 
the presence of hydroxyl is shown by the reaction with phos- 
phorus trichloride. We hence have C 2 H 3 O.OH as the formula 
representing this idea. But several questions still remain to be 
answered. There is another oxygen atom to be accounted for ; 
and the relations between the hydroxyl and this oxygen must 
be determined if possible. The fact that this second oxygen 
is not readily replaced by chlorine indicates that it is not 
present as hydroxyl, and all methods of testing for hydroxyl 
fail to show its presence in acet}^! chloride. Hence we may 
conclude that the second oxygen atom is present as carbonyl 


II 
CO. This leads us to the formula H — C — O — H for the simplest 

acid, or formic acid. Accordingly, formic acid appears as 

carbonic acid, which we commonly represent by the formula 

= C \ 5 in which one hydroxyl has been reduced to hydrogen. 

We have already seen that this reduction can be accomplished 
without difficulty. Many other arguments might be brought 
forward in favor of the view that the above formulas express 
the relations between formic and carbonic acids. Now, as 
acetic acid is the homologue of formic acid, we have every 



64 DERIVATIVES OF METHANE AND ETHANE. 

reason to believe that it differs from the latter in that it con- 
tains methyl in place of the hydrogen, which is in direct com- 
bination with carbon. It must hence be represented by the 



II CH 

formula CH 3 .C — OH or CO ( 3 . The common constituent of 

x OH 

II 
the two acids, is the group C — — H or —CO. OH, which is gener- 
ally known as carboxyl. Acetic acid is closely related not only 
to formic but to carbonic acid. It may be regarded as carbonic 

acid, CO \ 3 in which one hydroxyl is replaced by the radical 

OH 
methyl. In a similar way we shall see that all organic acids 
may be regarded as derived either from formic acid or from 
carbonic acid. 

Representing now the simplest hydrocarbon, alcohol, alde- 
hyde, and acid, by the structural formulas deduced from the 
facts, we have 




O fO 

C-! H C\ OH. 



OH 

H 

. H 

L H ^H ^H 

Methyl alcohol. afdThyde. Formic acid. 

Concerning the mechanism of the changes caused by oxida- 
tion, but little can be determined b}' experiment. We may 
regard methyl alcohol as the first and simplest product of 
oxidation of marsh gas. Starting with methyl alcohol, we 
might expect the next change to consist in the .introduction 

OH 



of another oxygen atom, giving a body cJ 0H . But it has 

I H 

u 

been found that, except under certain peculiar conditions, 
one carbon atom cannot hold two hydroxy Is in combination, 



RELATIONS BETWEEN COMPOUNDS OF CARBON. 65 

and that, if such a body is formed, it loses the elements of 
r OH 

water; thus, C j H = CN h+H 2 0. The result would be the 

aldehyde. This kind of change is illustrated in the formation 
of carbon dioxide from the salts of carbonic acid. Instead of 

OH 
getting the acid CO < , which we should naturally expect, we 

get this minus water : — 

(JM 

Now, when the aldehyde is oxidized, another oxygen atom is 
introduced, and the substance thus produced is an acid, or the 
hydroxyl hydrogen can be replaced by metals, and has in general 
the characteristics of acid Irydrogen. As soon as we have car- 
bon in combination with oxygen as carbonyl, and also with 
hydroxyl, the substance containing the combination is an acid. 

If, finally, the acid C 1 OH is oxidized, it is probable that the 
(H 
same change takes place as when the alcohol is oxidized. That 

is to say, the hydrogen is probably replaced by hydroxyl, when 
a compound containing two hydroxyls in combination with one 
carbon atom would be the result. This would be ordinary car- 
bonic acid. But this breaks up into water and carbon dioxide, 
which, as we know, are the products of oxidation of formic 
acid. 

All the many representatives of the great classes of carbon 
compounds known as the alcohols, aldehydes, and acids are 
closely related to the three fundamental substances, methyl 
alcohol, formic aldehyde, and formic acid. Replace one of 
the Irydrogen atoms of methyl alcohol by a radical, and we get a 

r OH 

H 
new alcohol, which may be represented by the formula C \ H • 

I R 
So also a similar replacement of a hydrogen atom in formic 



$6 DERIVATIVES OF METHANE AND ETHANE. 



, C J H ; and, 
Ir 



aldehyde gives another aldehyde, cJ H; and, finally, as we have 

IE 
seen, the acids of carbon may be represented by the formulas 

C ) OH or R.CO.OH, or CO < R , which show their relations to 

(B oh' 

formic and carbonic acids. Hereafter, in writing the formulas 
of members of the three great classes, the structure will be repre- 
sented by writing the hydroxyl group OH, the aldehyde group 
CHO, and the carboxyl group CO. OH or C0 2 H, separately 
from the rest of the formula. 



5. Ethereal Salts or Compound Ethers. 

Whenever an acid acts upon an alcohol, the acid is neutralized 
either wholly or partly, and a product analogous to the salts is 
formed. Thus nitric acid and ethyl alcohol give ethyl nitrate : — 

C 2 H 5 .OH + HN0 3 = C 2 H 5 .N0 3 + H 2 0, 

just as nitric acid and potassium hydroxide give potassium 
nitrate. It has been pointed out that the radicals, methyl, CH 3 , 
and ethyl, C 2 H 5 , take the part of metals in the ethereal salts. 
We can thus get a series of methyl and ethyl salts with the 
various acids. 

As regards the preparation of these compounds, it should be 
remarked that the action between an alcohol and an acid does 
not take place as readily as that between an acid and a metallic 
hydroxide. Only a few of the strongest acids act directly 
without aid. Such, for example, are nitric and sulphuric acids, 
though even the latter is not completely neutralized by action 
upon alcohols, as has already been seen in the preparation of 

C H 

ethyl-sulphuric acid, 2 D > S0 4 , for the purpose of making ether. 

Plainly ethyl- sulphuric acid is an acid ethereal salt, analogous 
to acid potassium sulphate. Both are still acid, though both 
are likewise salts. 



ETHEREAL SALTS. 67 

The methods which may be used for preparing ethereal salts 
are the following : — 

(1) Treatment of an acid with an alcohol. This is capable 
of only very limited application, as in the case of a few of the 
strongest acids. 

(2) Treatment of the chloride of an acid with alcohol. This 
has been illustrated by the action of acetyl chloride, C 2 H 3 0.C1, 
upon methyl alcohol (see p. 62) : — 

C 2 H 3 0C1 + HO.CH 3 = C 2 H 3 O.OCH 3 + HC1, 
or CH 3 .COCl + HO.CH 3 = CH 3 .COOCH 3 + HC1. 

(3) Treatment of the silver salt of an acid with a halogeu 
substitution-product of a hydrocarbon. For example, ethyl 
acetate can be made by treating silver acetate with brom- 
ethane : — 

CH 3 .COOAg + C 2 H 5 Br = CH 3 COOC 2 H, + AgBr. 

This reaction is well adapted to showing the relation between 
the salt and the ethereal salt, and leaves no room for doubt that 
the two are strictly analogous. 

(4) Treatment of a mixture of an alcohol and an acid with 
dry hydrochloric acid gas or strong sulphuric acid. The forma- 
tion of ethyl acetate b}' this method was illustrated in Experi- 
ment 19, p. 60. The sulphuric acid facilitates the action by 
uniting with the alcohol to form ethjl-sulphuric acid, which with 
the acid gives the ethereal salt : — 

C2 ^ 3 >S0 4 + CH 3 .COOH = CH 3 .COOC 2 H 5 + H 2 S0 4 . 

It is probable that the hydrochloric acid first acts upon the 
acid forming the chloride, and that this then acts upon the 
alcohol, forming the ethereal salt : — 

CH 3 .COOH + HC1 = CH 3 .COCl + H 2 ; 
CH 3 .COCl + C 2 H 5 OH = CH 3 .COOC 2 H 5 + HC1. 



68 DERIVATIVES OF METHANE AND ETHANE. 

Among the more important ethereal salts of methyl and ethyl 
alcohols, the following may be mentioned : — 

Methyl-sulphuric acid, H 3 > S0 4 , formed by mixing- 
methyl alcohol and sulphuric acid. The acid itself, as well as 
its salts, is very easily soluble in water. 

Ethyl nitrate, 2 H 5 NO 3 , formed by treating alcohol with 
nitric acid. Unless precautions are taken in mixing these 
reagents, complete decomposition of the alcohol will take place, 
and the action will be accompanied by a violent explosion. 

Ethyl-sulphuric acid, 2 fz 5 > S0 4 . Made in the same way 

XX 

as the methyl compound. The acid and its salts are easily sol- 
uble in water. When boiled with water it is decomposed, 
yielding alcohol and sulphuric acid : — 

° 2 !! 5 >S0 4 + H 2 = H 2 S0 4 + C 2 H 5 OH. 

XX 

Ethyl sulphate, (0 2 H 5 ) 2 SO 4 , is made by passing the vapor 
of sulphur trioxide into well-cooled ether : — 

(C 2 H 5 ) 2 + S0 3 = (C 2 H 5 ) 2 S0 4 . 

Phosphoric acid yields ethyl phosphate, (C 2 H S ) 3 P0 4 , di-ethyl-phos- 
phoric acid, (C 2 H 5 ) 2 HP0 4 , and ethyl-phosphoric acid, C 2 H 5 H 2 P0 4 . 

There also are similar derivatives of arsenic, boric, silicic, and 
other mineral acids. 

Of the ethereal salts which the two alcohols form with formic 
and acetic acids, methyl and ethyl acetates are the best known. 
The methods of preparing them have already been considered. 
They are both liquids having pleasant odors. This is indeed a 
characteristic of many of the volatile ethereal salts of the acids 
of carbon, and many of the odors of fruits and flowers are due 
to the presence of one or another of these compounds. Many 



SAPONIFICATION. 69 

of them also are used for flavoring purposes instead of the 
natural substances. 

Experiment 22. Make a mixture of 15 parts (150s) of ordinary 
concentrated sulphuric acid and 6 parts (60s) absolute alcohol. Add 
to it 10 parts (100s) sodium acetate. Distil from a flask. Redistil 
the distillate. The ethyl acetate thus formed boils at 77°. What 
reactions take place in this case? 

Decomposition of ethereal salts. Salts of most metals are 
decomposed when treated with an alkaline hydroxide, as caustic 
soda or caustic potash, the result being a salt of the alkali and 
the hydroxide of the replaced metal, as seen in the case of 
copper sulphate and sodium lrydroxide : — 

CuS0 4 + 2NaOH = Cu(OH) 2 + Na 2 S0 4 . 

So also the ethereal salts are decomposed when treated with the 
alkalies, though, as a rule, not as readily as salts. It is usually 
necessary to boil the ethereal salt with the alkali when decom- 
position takes place, the radical, like the metal, appearing in 
the form of the hydroxide or alcohol, and the alkali metal taking 
its place. Thus, when ethyl sulphate is treated with a solution 
of caustic potash, this reaction takes place : — 

(C,H 5 ) 2 S0 4 + 2 KOH = K 2 S0 4 + 2 C 2 H 5 .OH ; 

and when ethyl acetate is treated with caustic soda, we have this 
reaction : — 

CH 3 .COOC 2 H 5 + NaOH = CH 3 .COONa -f- C 2 H 5 OH. 

Experiment 23. In a 500 cc flask put 200 cc water, 50s solid 
caustic potash, and 20 cc ethyl acetate. Counect with an inverted con- 
denser, arranged as shown in Fig. 8. Boil gently for half au hour. 
Now connect the condenser with the flask for distilling, and again boil. 
Examine the distillate for alcohol. Acidify the contents of the flask 
with sulphuric acid, and again distil. What passes over? 

All ethereal salts are decomposed by boiling with the caustic 
alkalies. As this decomposition is best known on the large scale 
in the preparation of soaps, it is commonly called saponification. 



70 



DERIVATIVES OF METHANE AND ETHANE. 



As will be shown, the fats are ethereal salts, and soap-making 
consists in decomposing these fats by means of the alkalies. 
Hence, generally, to saponify an ethereal salt means to decom- 
pose it by means of an alkali into the corresponding alcohol and 
the alkali salt of the acid contained in it. 




6. Ketones or Acetones. 

When an acetate is distilled, a liquid passes over which has 
fche composition C 3 H 6 0, and a carbonate remains behind. The 
reaction has been carefully studied, and has been shown to take 
place in accordance with the following equation : — 

CH3.C00 c = CH0 + CaC o 3 . 

CH3.COO 3 6 t 3 

The substance C 3 H 6 is known as acetone. It is the best 
known representative of a class of bodies which are sometimes 
called acetones, but more commonly ketones. 

Acetone, 3 H 6 O. — This substance has long been known 
as a product of the distillation of acetates. It is contained 
in considerable quantities in the product obtained in the 



ACETONE. 71 

distillation of wood, and can be separated from the mixture 
after the removal of the acetic acid. 

It can be purified by shaking a mixture containing it with a 
concentrated solution of mono-sodium sulphite. It unites with 
the salt, forming a compound analogous to that formed with 
aldehyde. The double compound can be separated, and when 
distilled with the addition of potassium carbonate acetone passes 
over. 

Acetone is a colorless liquid having a penetrating pleasant 
ethereal odor. It boils at 56.3°. It is a good solvent for many 
carbon compounds, such as resins, fats, etc. 

On studying the conduct of acetone, it soon becomes evident 
that it more closely resembles the aldehydes than airy other 
bodies thus far considered. It is plainly not an acid nor an 
alcohol. It acts eutirely differently from either. It is not an 
ethereal salt, for on boiling with an alkali it does not yield an 
alcohol nor the salt of an acid. On the other hand, it unites 
with the acid sulphites like the aldehydes. Further, when 
treated with phosphorus pentachloride its oxygen is replaced by 
two chlorine atoms thus : — 



C 3 H 6 + PC1 5 = C 3 H 6 C1 2 + POC1 



- 3 ; 



and when treated with nascent hydrogen, it is converted into a 
substance -having alcoholic properties. These facts lead to 
the conclusion that the substance contains carbonyl, CO, as the 
aldehydes do. This is shown in the formula C 2 H 6 CO. The 
formation from calcium acetate leads further to the belief that 
the group C 2 H 6 really consists of two methyls, as the simplest 
interpretation of the reaction is represented thus : — 

CH!cOO >Ca = S >C ° + CaC ° 3 - 

According to this, acetone is a compound of two metlryl groups 
and carbonyl, or it is carbon monoxide whose two available 
affinities have been satisfied by two methyl groups. 



72 DERIVATIVES OF METHANE AND ETHANE. 

We can test the correctness of this view by means of synthe- 
ses. If it is correct, it will be seen that acetone is closely 
related to acetyl chloride. It is acetyl chloride in which the 
chlorine has been replaced b} r methyl : — 

CH3.CO.Cl CH3.CO.CH3. 

Acetyl chloride. Acetone. 

Now, when acetyl chloride is treated with zinc methyl, Zn(CH 3 ) 2 , 
it yields acetone according to this equation : — 

2 CH3.COCI + Zn(CH 3 ) 2 = 2 CH3.CO.CH3 -f ZnCl 2 . 

Further, acetone can be made by treating carbon monoxide 
with sodium methyl, a direct addition of two methyl groups to 
carbon monoxide being thus effected. The relation between 
acetone ant 1 ordinary acetic aldehyde is like that of an ethereal 
salt to its acid ; that is, acetone is aldehyde, CH 3 .COH, in 
which the hydrogen has been replaced by methyl, CH 3 .CO.CH 3 . 

Like the aldehydes, the acetone has the power of taking up 
other substances, such as the acid sulphites, ammonia, hydro- 
cyanic acid, hydrogen, etc. This power is in some way con- 
nected with the relation of the oxygen to the carbon, which is 
the same in both compounds. Nevertheless, this condition of 
the oxygen does not always carry with it the same power as 
seen in the case of the acids which also contain carbonyl. 

By reduction with nascent hydrogen, acetone yields an alco- 
hol of the formula C 3 H 8 0, known as secondary propyl alcoJiol, 
which when oxidized yields acetone. In other words, the rela- 
tion between this alcohol and acetone is much the same as that 
between ethyl alcohol and acetic aldehyde. But while the alde- 
hyde by further oxidation yields acetic acid by simply taking 
up one atom of oxygen, acetone is decomposed by oxidizing 
agents, and yields acetic and carbonic acids. Towards oxidiz- 
ing agents, then, acetones (for it will be shown that other 
acetones conduct themselves in the same way) act entirely 
differently from the aldehydes. The alcohol above mentioned 



GENERAL STATEMENTS. 73 

as related to acetone is the simplest representative of a class of 
alcohols differing in some respects from the substances com- 
monly called alcohols. 



We have thus considered the most important representatives 
of six classes of oxygen derivatives of the hydrocarbons, and, 
by a study of their chemical conduct and the methods available 
for their preparation, have formed views in regard to the rela- 
tions between them. In our ordinary language we may express 
these relations briefly thus : The alcohols are the hydroxyl 
derivatives of the hydrocarbons or the hydroxides of certain 
groups called radicals; the ethers are the oxides of these same 
radicals ; the aldehydes are compounds consisting of carbonyl, 
hydrogen, and a radical ; the acids are compounds of carbonyl, 
hydroxyl, and a radical, or, better, they are carbonic acid in 
which hydrogen and oxygen, or hydroxyl. have been replaced 
by a radical ; the ethereal salts are compounds like ordinary 
metallic salts, only they contain a radical in the place of the 
metal ; and, finally, the ketones are aldehydes in which the 
distinctively aldehyde hydrogen has been replaced by a radical, 
or they are compounds consisting of carbonyl and two radicals. 

These ideas are expressed in formulas thus, R being any 
univalent radical like methyl, CH 3 , or ethyl, C 2 H 5 : — 

Alcohol .... R-O-H. 
Ether R-O-R. 

Aldehyde. . . . R-C-H. 

I! 

o 

Acid R-C-O-H. 

II 

O 
Ethereal salt . . Ac — O — R (Ac — O — H representing any 
monobasic acid). 

Ketone .... R-C-R. 

II 
O 



CHAPTER V. 

SULPHUR DERIVATIVES OP METHANE AND 
ETHANE. 

1. Mercaptans. 

The simplest derivatives of methane and ethane containing 
sulphur are the so-called mercaptans or sulphur alcohols. They 
can be made by a method similar to one described under the 
head of Alcohols. When a mono-halogen derivative of a hydro- 
carbon, as brom-methane, CH 3 Br, is treated with the hydroxide 
of a metal, as silver hydroxide, AgOH, an alcohol is formed : — 

CH 3 Br + AgOH = CH 3 OH + AgBr. 

So, also, when a similar halogen derivative is treated with a 
liydrosulphide instead of a hydroxide, a compound is obtained 
which we may regard as an alcohol in which the oxygen has 
been replaced by sulphur : — 

CH 3 Br + KSH = CH 3 SH + KBr. 

The compound is called a mercaptan. 

Ethyl-mercaptan, C 2 H 5 . SH. — This substance can be pre- 
pared by treating iodo-ethane, C 2 H 5 I, with an alcoholic solu- 
tion of potassium liydrosulphide, KSH ; also by distilling a 
mixture of the concentrated solutions of potassium ethylsul- 
phate and potassium liydrosulphide : — 

C 2 H 5 > SQi + KSH = KS()4 + CaHjjSH# 
K 

It is a liquid of an extremely disagreeable odor; it boils at 37° , 
and is difficultly soluble in water. 



ETHYL-MERCAPTAN. 75 

The name " mercaptan " was given to it on account of its 
action towards mercury. It readily forms a compound in which 
mercury takes the place of hydrogeu, (C 2 H 5 S) 2 Hg; and the 
name has reference to this power {corpus mercuric- aptum) . It 
forms many other well-characterized metallic derivatives like 
this mercury compound. 

When the sodium compound of mercaptan is exposed to the 
air, it takes up oxygen. So, also, when mercaptan itself is 
treated with nitric acid, it is oxidized, the product having the 
formula C 2 H 5 . S0 3 H. It will thus be seen that, though in com- 
position mercaptan is analogous to alcohol, towards oxidizing 
agents it conducts itself quite differently. In the case of alco- 
hol two atoms of Irydrogen are replaced by one of oxygen. In 
the case of mercaptan three atoms of oxygen are added directly 
to the molecule. It will be shown that this new acid, which is 
called ethyl- sidpJionic acid, bears to sulphuric acid a relation 
similar to that which acetic acid bears to carbonic acid ; and 
that it bears to sulphurous acid a relation similar to that which 
acetic acid bears to formic acid. 

When treated with phosphorus pentachloride it yields a chlo- 
ride, C 2 H 5 .S0 2 C1 ; and, when this is treated with nascent hydro- 
gen (zinc and hydrochloric acid) , it is reduced to mercaptan : — 

C 2 H 5 .S0 2 C1 -f 6H = C 2 H 5 .SH + HC1 + 2 H 2 0. 

2. Sulphur Ethers. 

There are compounds known similar to the ethers, containing 
sulphur in the place of the oxygen of the ethers. Such are 
methyl-sulphide, (CH 3 ) 2 S, and ethyl-sulphide, (C 2 H 5 ) 2 S. These 
are made by treating brom- or iodo-methane or ethane with 
potassium sulphide : — 

2 C 2 H 5 I + K 2 S = (C 2 H 5 ) 2 S + 2 KL 

They are liquids of very disagreeable odors. 



76 DERIVATIVES OF METHANE AND ETHANE. 

3. Sulphonic Acids. 

It was stated above, that when mercaptan is oxidized it is 
converted into an acid of the formula C 2 H 5 . S0 3 H, or ethyl-sul- 
phonic acid. This is the representative of a large class of sub- 
stances which are commonly made by treating carbon compounds 
with sulphuric acid. These sulphonic acids can best be studied 
in connection with another series of hydrocarbons. UDder the 
head of Benzene (which see) it will be shown that, when this 
hydrocarbon is treated with sulphuric acid, a reaction takes, 
place which may be represented thus : — 

C 6 H 6 + ™ > S0 2 = ^ > S0 2 + H 2 0. 

Benzene. Benzene-sulphonic acid. 

The sulphonic acid thus obtained can also be made by oxi- 
dizing the corresponding mercaptan or hydrosulphide, C 6 H 5 . SH. 
Accordingly, the sulphonic acid appears to be sulphuric acid in 
which a hydroxyl has been replaced by the radical C 6 H 5 . Sea- 
soning by analogy, which, fortunately, is supported by other 
arguments, we may conclude that ethyl-sulphonic acid formed 

from ethyl-mercaptan bears a similar relation to sulphuric acid, 

C TT 
and corresponds to the formula ^a 5 > S0 2 . So, also, methyl- 

sulphonic acid obtained by oxidation of methyl-mercaptan 

should be represented by the formula -rr^ 3 > S0 2 or CH 3 . S0 2 OH. 

Its relation to sulphuric acid is the same as that of acetic acid to 
carbonic acid. 

Another method by which the sulphonic acids can be pre- 
pared consists in treating a sulphite with a halogen substitu- 
tion-product. Thus ethyl-sulphonic acid can be prepared from 
potassium sulphite and iodo-ethane : — 



K > SO, = C2H5 
K 3 K 



C 2 H 5 I + _>S0 3 =^_ 5 >S0 3 + KI, 



or C 2 H 5 I + ^ > S0 2 = °A > S0 2 + KL 



SULPHONIC ACIDS. 77 

According to this reaction the sulphonic acids appear to be 
identical with the ethereal salts of sulphurous acid, but they 
do not conduct themselves like ethereal salts. The differ- 
ence is particularly noticeable in connection with the stability, 
the sulphonic acids as a class being much more stable than 
the ethereal salts as a class. At present it would be some- 
what premature to discuss fully the question as to their rela- 
tions. Whatever we may call them, they are closely related to 
sulphurous acid, and are derived from it by replacement of 
hydrogen by a radical, just as acetic acid may be regarded as 
derived from formic acid by replacement of hydrogen by a 
radical. These relations are represented by the following 
formulas : — 

Carbonic acid, CO < . Sulphuric acid, S0 2 < 

OH OH 

TT TT 

Formic acid, CO < . Sulphurous acid, S0 2 < 

OH OH 

Acetic acid, CO < ^ 3 . Methyl-sulphonic acid, S0 2 < CU \ 
OH OH 

Any carbonic | C0 B Any sulphonic acid, S0 2 < R . 

acid, J OH J F OH 

The difference between a sulphonic acid and an ethereal salt of 
sulphuric acid should be specially noticed. Compare for this 

C H O 
purpose ethyl-sulphuric acid, 2 JL > S0 2 , and ethyl-sulphonic 

C H 
acid, * 5 > s0 2- Both are monobasic acids, and both contain 
HO 

ethyl, but there is a difference of one atom of oxygen in their 
composition. The reactions of the substances are such as to 
lead to the conclusion that in ethyl-sulphonic acid the ethyl 
group is directly connected with the sulphur ; and that in 
ethyl-sulphuric acid the connection is established by means of 
oxygen. The strongest argument in favor of this view is 
perhaps that which is founded on the formation of the sulphonic 
acids by oxidation of the hydrosulphides or mercaptans. It 



78 DERIVATIVES OF METHANE AND ETHANE. 

can hardly be doubted that in ethyl mercaptan the sulphur is in 
direct combination with the ethyl ; or, to go still farther, that 
it is in combination with carbon as represented in the formula 

H 
H 3 C — C — S — H. Now, by oxidation of mercaptan, three atoms 

H 
of oxygen are added, and the simplest view we can take of the 
reaction is that the sulphur is left undisturbed in its relations to 
ethyl, but that it has taken up the oxygen, as represented in the 
formula C 2 H 5 — S0 2 .OH. As has been shown, the oxygen can 
be removed again by nascent hydrogen, and the result is mer- 
captan. The study of the sulphonic acids in their relations to 
sulphuric and sulphurous acids has been of considerable assist- 
ance in enabling chemists to form conceptions in regard to the 
relations of the constituents of the two latter. The view which 
is forced upon us by a consideration of the reactions described 
above is that sulphurous acid differs from sulphuric acid in 
containing a hydrogen atom in place of Irydrox}!, as represented 

OH H 

in the formulas S0 2 < TJ and SO., < ; and, further, that in 
OH " OH 

sulphurous acid one hydrogen is in- combination with sulphur 

and the other with oxygen. 



CHAPTER VI. 

NITROGEN DERIVATIVES OP METHANE AND 
ETHANE. 

The simplest compounds of carbon containing nitrogen are 
cyanogen and lrydroc3'anic acid. Strictly speaking, neither can 
be regarded as a derivative of a hydrocarbon, unless indeed we 
consider hydrocyanic acid as marsh gas, in which three hy dro- 
ll 



TT 

gen atoms have been replaced by one nitrogen : C -j and 

1h 

C I . That, however, is a mere matter of words, as there is 
( H 

nothing in the conduct of either substance, or in the methods of 
formation of hydrocyanic acid, that would lead us to suspect 
any relation between them. Though cyanogen and hydrocyanic 
acid are therefore not to be considered as derivatives of the 
hydrocarbons, they form the starting-point for the preparation 
of so many important compounds that they and their simpler 
derivatives must receive some consideration at this stage. 

Cyanogen, (CN) 2 . — All organic compounds that contain 
nitrogen give sodium cyanide when ignited with sodium. So, 
also, potassium cyanide is formed when charcoal containing 
nitrogen is heated with potassium carbonate. Cyanogen itself 
is most readily made by heating mercuric cyanide, Hg(CN) 2 . 
The decomposition that takes place is, in the main, like the 
simple decomposition of mercuric oxide in preparing oxygen : — 

Hg(CN) 2 =Hg + (CN) 2 ; 
HgO = Hg + O. 



80 DERIVATIVES OF METHANE AND ETHANE. 

But, in heating mercuric cyanide, a black solid substance, para- 
cyanogen, is formed, and remains behind in the 'retort. It has 
the same composition as cyanogen, and is therefore a polymeric 
modification. 

Cyanogen (from kvolvos, blue) owes its name to the fact that 
several of its compounds have a blue color. It is a colorless 
gas, which is easily soluble in water and alcohol, and is ex- 
tremely poisonous. It burns with a purple-colored flame. 
. In aqueous solution, cyanogen soon undergoes change, and a 
brown amorphous body is deposited. In the solution are found 
hydrocyanic acid, oxalic acid, ammonia, and carbon dioxide. 
A little dilute acid prevents this decomposition. 

Hydrocyanic acid, HON. — This acid, which is commonly 
called prussic acid, occurs in nature in amygdalin in combi- 
nation with other substances, in bitter almonds, the leaves of 
the cherry, laurel, etc. It is prepared by decomposing metal- 
lic cyanides with hydrochloric acid, as represented in the equa- 
tion : — 

KCN + HC1 = KC1 + HCN. 

It can also be made by treating chloroform with ammonia : — 

CHCI3 + NH 3 = HCN + 3 HC1, 
or CHCI3 + 5 NH 3 = NH 4 . CN + 3 NH 4 C1. 

It is a volatile liquid, boiling at 26.5°, which solidifies at —15°. 
It has a very characteristic odor, suggesting bitter almonds. It 
is extremely poisonous. It dissolves in water in all proportions, 
and it is this solution which is known as prussic acid. Pure 
hydrocyanic acid is very unstable. By standing, a brown sub- 
stance is deposited. By boiling with alkalies or acids, it is 
converted into formic acid and ammonia (see p. 56). 

Hydrocyanic acid can be detected 03^ the fact that when its 
solution is saturated with caustic potash, and a solution contain- 
ing a ferrous and a ferric salt is added, a precipitate of Prussian 



POTASSIUM FERBOCYANIDE. 81 

blue is formed ; or, by adding yellow ammonium sulphide to its 
solution, evaporating off the excess of ammonium sulphide, and 
then adding a drop of solution of ferric chloride. If hydrocy- 
anic acid was present, the solution turns a deep blood red. 

Cyanides. — Hydrocyanic, like hydrochloric acid, forms a 
series of salts, which are called the cyanides. The cyanides of 
the alkali metals and of mercury are soluble in water. The 
cyanides of the heavy metals have a marked tendency to form 
double cyanides, and those double cyauides which contain an 
alkali metal are soluble in water. Hence, the precipitates 
formed by potassium cyanide, in solutions containing the heavy 
metals, are dissolved by excess of the cyanide. 

Among the best known double cyanides are the two salts, 
potassium ferrocyanide and potassium ferricyanide. The former 
is commonly called yellow prussiate of potash, and the latter 
red prussiate of potash. 

Potassium ferrocyanide, 4 KCN.Fe(CN) 2 + 3 H,0. — 
This salt is made on the large scale by melting together, in iron 
vessels, refuse animal substances {i.e., organic matter contain- 
ing nitrogen) with potassium carbonate and iron. The mass is 
treated with water, and the salt which is thus extracted puri- 
fied by crystallization. 

It crystallizes in large 3-ellow crystals, and is soluble in about 
four parts of water at 15°. 

When ignited, it breaks up according to this equation : — 

4 KCN.Fe(CN) 2 = 4 KCN + FeC 2 -f N 2 . 

This decomposition is made use of for the purpose of preparing 
potassium cyanide. As, however, a portion of the cyanogen is 
lost in this way, potassium carbonate is generally added, when 
the reaction represented by the following equation takes 
place : — 

4 KCN. Fe(CN) 2 + K 2 C0 3 = 5 KCN + KCNO +■ C0 2 + Fe. 



82 DERIVATIVES OF METHANE AND ETHANE. 

The potassium cyanide made in this way always necessarily con- 
tains potassium cyanate, KCNO. 

Experiment 24. l Make a mixture of 8 parts (1608) dehydrated 
potassium ferrocyanide aud 3 parts (60s) dry potassium carbonate. 
Fuse in an iron crucible, at a low red heat, until a specimen taken 
out and placed on a stone is white when solid. Then pour out on a 
flat, smooth stone, and afterwards break up and put in a dry bottle. 

When treated with dilute sulphuric acid, the fenx^anide 
yields hydrocyanic acid thus : — 

2 [4 KCN.Fe(CN) 2 ] + 3 H,S0 4 

= 6HCN + 2[KCN.Fe(CN) 2 ] + 3 K 2 S0 4 . 

This reaction is the one actually made use of for the prepara- 
tion of hydrocyanic acid. 

Potassium ferrocyanide is the starting-point for the prepara- 
tion of all compounds containing C3 T anogen. 

Potassium ferricyanide, 3 KCN.Fe(CN) 3 - — This salt, 
known as red prussiate of potash, is prepared by oxidizing the 
ferrocyanide. 

Experiment 25. Dissolve 26s potassium ferrocyanide in 200 cc cold 
water, and add 8 CC ordinary concentrated hydrochloric acid. Into 
this pour slowly a cold solution of 2% of potassium permanganate 
in 300 cc water. The oxidation is complete when a drop added to 
ferric chloride gives a brownish-red color, but no precipitate. Neutral- 
ize with chalk, filter, and evaporate on a water-bath. 

Potassium ferricyanide is easily soluble in water, and crys- 
tallizes from its concentrated solutions in large, dark-red 
crystals belonging to the rhombic system. 

In alkaline solutions it is an excellent oxidizing agent. 

1 Experiments 24 and 26 may be postponed until urea is studied, when they may 
be combined with the artificial preparation of urea. 



CYANIC ACID. 83 

Reducing agents, such as hydrogen sulphide, sodium thio- 
sulphate (hyposulphite), etc., convert it into the yellow salt. 

Prussian blue, TurnbulVs blue, soluble Prussian blue, and 
Berlin green are complex cyanides of iron represented by the 
formulas 

4Fe(CN) 3 .3Fe(CN) 2 , 

3Fe(CN) 2 .2Fe(CN) 3 , 
KCN.Fe(CN) 3 .Fe(CN) 2 , 
and Fe 3 (CN) 8 + 4H 2 0, respectively. 

For a full account of the many compounds of the metals and 
cyanogen, the student is referred to larger works. 

Cyanogen chlorides. — When chlorine is allowed to act 
upon cyanides or dilute hydrocyanic acid, a volatile liquid is 
formed which has the composition represented by the formula 
CNC1. It boils at 15.5°, and its vapor acts upon the eyes, 
causing tears. It is known as liquid cya,nogen chloride to dis- 
tinguish it from solid cyanogen chloride. The latter has the 
formula (CN) 3 C1 3 , and is formed by treating anhydrous hydro- 
cyanic acid with chlorine in direct sunlight. The liquid variety 
is partially transformed into the solid when kept in sealed 
tubes. 

Similar compounds of cyanogen with bromine and iodine are 
known. 

Cyanic acid, CONH. — When a cyanide of an alkali is 
treated with an oxidizing agent, it takes up oxygen and is con- 
verted into a cyanate : — 

CNK + O = CONK. 

Experiment 26. 1 Heat a mixture of 8 parts (160s) dehydrated 
potassium ferrocyanide, and 3 parts(GOs) dry potassium carbonate in an 
iron crucible. When the transformation into the cyanide is complete 
(see Ex. 24, p. 82), take the crucible out of the furnace ; and, after it 

See Note, p. 82, 



84 DERIVATIVES OF METHANE AND ETHANE. 

has cooled down somewhat, but while the mass is still liquid, add 
gradually 15 parts (300s) red lead, stirring during the operation. Put 
the crucible again in the furnace for a little while ; allow the reduced 
lead to settle, and then pour out the contents on a smooth stone. After 
the mass is cold, break up and extract the cyanate with alcohol (of 86 
per cent). 

Cyanic acid is readily decomposed by water into ammonia 
and carbon dioxide : — 

CONH + H 2 = NH 3 + C0 2 . 

The potassium salt is easily soluble in water, but is easily 
decomposed by it, yielding ammonia and potassium carbon- 

CONK + 2 H 2 = KHC0 3 + NH 3 . 

The most interesting salt of cyanic acid is ammonium cyanate, 
CON.NH 4 . It can be made by adding ammonium sulphate to 
a solution of the potassium salt. It is easily soluble in water ; 
but, if allowed to stand in solution, or if its solution is heated, 
it is completely transformed into urea, which is isomeric with it. 
The interest connected with this transformation was referred to 
in the introductory chapter (p. 1) . It will be considered more 
fully under the head of urea. 

Cyanuric acid, C3N3H3O3. — This acid bears a relation to 
cyanic acid similar to that which solid cyanogen chloride, 
(CN) 3 C1 3 , bears to the liquid variety. It is made by treating 
the solid chloride with water, and also by heating urea. It is 
a crystallized substance. 

Sulpho-cyanic acid, CNSH. — Just as the C3 T anides of the 
alkalies take up oxygen and are converted into cyanates, so also 
they take up sulphur and are converted into sulpho-cyanates : — 

CNK + S = CNSK. 

Potassium 
eulpho-cyanate. 



SULPHOCYANIC ACID. 85 

Experiment 27. Melt together in an iron crucible 17 parts (85s) 
dry potassium carbonate and 32 parts (160s) sulphur, and then add 46 
parts (230s) powdered dehydrated potassium ferrocyanide. Keep the 
mass at a low red heat until the ferrocyanide is destroyed. After 
cooling, extract with water, neutralize the filtered solution with sul- 
phuric acid, evaporate, aud separate from potassium sulphate bj r means 
of alcohol. 

Potassium sulpho-cyanate crystallizes in long striated prisms 
without water of crystallization. It is deliquescent. When 
dissolved in water the temperature sinks markedly. When 100 
parts of water of 10.8° are mixed with 150 parts of the salt, the 
temperature sinks to — 23.7°. By evaporation of the solution, 
the salt can be recovered. 

Experiment 28. Dissolve some potassium sulpho-cyanate in water, 
and note the temperature before aud after introducing the salt. 

Ammonium sulpho-cyanate. CNS.NH 4 . This salt is most 
easily prepared by treating carbon disulphide with a solution of 
ammonia in dilute alcohol : — • 

CS 2 + 4NH 3 = CNS.NH 4 + (NH 4 ) 2 S. 

Experiment 29. Mix 240 cc strong aqueous ammonia, 240 cc alcohol, 
and 60s carbon disulphide. Allow the mixture to stand for one or 
more days. Then distil clown to oue-third of the original volume, and 
filter while still hot the solution left in the flask. On cooling, ammo- 
nium sulpho-cyanate will crystallize out. 

The salt crystallizes in plates. It melts at 160° (try it), 
and at 170° it is transformed into the isomeric substance known 
as sulpho-urea. (Analogy to transformation of ammonium 
cyanate.) 

Having thus considered some of the more important simpler 
C}'anogen compounds, we may now return to the nitrogen deriv- 
atives of the hydrocarbons. For convenience, these may be 
divided into three classes : — 

(1) Those which are related to cyanogen; 

(2) Those which are related to ammonia; 

(3) Those which are related to nitric acid. 



86 DERIVATIVES OF METHANE AND ETHANE. 

Cyanides. 

Methyl cyanide, CH 3 .CN. — This compound is formed by 
distilling a mixture of potassium methyl-sulphate and potas- 
sium cyanide : — 

C ^ 3 >S0 4 + KCN = K 2 S0 4 + CH 3 CN. 

It is a liquid boiling at 82°. 

According to the method of preparation, it must be regarded 
as an ethereal salt of hydrocyanic acid, containing methyl in the 
place of the potassium of the potassium salt. 

Ethyl cyanide, C 2 H 5 .CN. — Formed like the methyl com- 
pound. Also by heating chlor-ethane with potassium cya- 
nide : — 

C 2 H 5 C1 + KCN = C 2 H 5 .CN + KC1. 

It is a liquid boiling at 98°. 

The two most characteristic reactions of these cyanides are 
(1) that which is effected by caustic alkalies, and (2) that 
effected by nascent hydrogen. 

When methyl cyanide is treated with caustic potash, it yields 
acetic acid and ammonia : — 

s CH 3 .CN + H 2 + KOH = CH 3 .C0 2 K + NH 3 . 

This reaction is strictly analogous to that which takes place 
with hydroc3*anic acid yielding formic acid (see p. 56). In 
the same way ethyl cyanide yields an acid of the formula 
C 3 H 6 2 (or C 2 H 5 .C0 2 H). Thus, 03^ making a cyanide, we have 
it in our power to make an acid containing the same number of 
carbon atoms. 

This reaction, therefore, enables us to pass from an alcohol 
to an acid containing one atom of carbon more than the alcohol 
contains. It has been of great service in the study of the com- 
pounds of carbon. 



ETHYL CYANIDE. 87 

Note for Student. — Show how, by starting with methyl alcohol, 
acetic acid may be made by passing through the cyanide. 

There are two ways in which the cyanogen group can be 
linked to methyl in methyl cyanide ; viz., either by the carbon 
atom, as represented in the formula H 3 C — C — N, or by the 
nitrogen atom, as represented thus, H 3 C — N — C. The ease 
with which the nitrogen is separated from the compound, leav- 
ing the two carbon atoms united, as shown in the reaction with 
caustic potash, naturally leads to the conclusion that the for- 
mer view is the correct one. If it is correct, it would appear 
to follow that in potassium cyanide the potassium is in combi- 
nation with carbon as represented in the formula K— C— N, 
and further that in hydrocyanic acid the hydrogen is in combi- 
nation with carbon, as shown thus, H — C— N. 

In consequence of the close relation existing between the 
cyanides and the acids, the former are frequently spoken of as 
the nitrites of the acids. Thus methyl cyanide, which is con- 
verted into acetic acid by boiling with caustic potash, is called 
the nitrile of acetic acid, or aceto -nitrite. In the same way 
hydrocyanic acid itself niay be regarded as the nitrile of formic 
acid, or formo -nitrile. 

When methyl cyanide is treated with nascent Irydrogen, it is 
converted into a substance which closely resembles ammonia, 
and is known as ethyl-amine. It will be shown to bear to 

(C 2 H 5 
ammonia the relation indicated by the formula N ) H ; i.e., it 

is ammonia in which one hydrogen has been replaced by ethyl. 
The reaction may be represented by the equation : — 

/ ( H \ 

H 3 C-C-N + 4 H = H 3 C-H 2 C-NH 2 1 or N ] h ' • 

This transformation strengthens the conclusion already reached, 
that the two carbon atoms in methyl c}'anide are directl}' united. 
If this were not the case, it is difficult to see how a compound 



88 DERIVATIVES OF METHANE AND ETHANE. 

containing etlryl in which the two carbon atoms are unquestion- 
ably united, could be formed so easily from it. 

Just as methyl cyanide yields ethyl-amine when treated with 
nascent hydrogen, so hydrocyanic acid yields methyl-amine 

( CH 3 

n)h : — 

<h / rcH 3 \ 

H-C-N + 4H = H 3 C-NH 2 or N J H l 

The amines, or substituted ammonias, will be considered more 
fully hereafter. 

ISOCYANIDES OR CaRBAMINES. 

If, in making an ethereal salt of hydrocyanic acid from a salt, 
the silver salt is used, a compound is obtained having the same 
composition as the cyanide, but differing very markedly from 
it. The substance thus obtained is called an isocyanide or car- 
bamine. 

Ethyl isocyanide or ethyl carbamine, 2 H 5 .NC. — This 

compound is obtained when silver cyanide and iodo-ethane are 
heated together : — 

C 2 H 5 I + AgNC = C 2 H 5 NC + Agl. 

It is also formed when chloroform and ethyl-amine (see above) 
are brought together : — 

/-rirr 

CHC1 3 + N ] h * = C 2 H 5 NC + 3 HC1. 

It is a liquid boiling at 79°. It is characterized by an unbear- 
able, indescribable odor. The methyl compound obtained by 
the same method boils at 58° to 59°, but otherwise has proper- 
ties almost identical with those of ethyl isocyanide* 



ETHYL ISOCYANIDE. 89 

The reactions of these substances are quite different from 
those of the cyanides. They are decomposed only with great 
difficulty bj' the caustic alkalies ; but, when brought together 
with hydrochloric acid, they undergo an interesting change, 
which may be represented by the following equation for the 
methyl compound : — 

CH 3 .NC + 2H 2 = CH 3 -NH 2 + H.C0 2 H. 

Methyl-amine. Formic acid. 

This reaction indicates that in the isocyanides the cyanogen 
group is urited to the radical by means of nitrogen, as repre- 
sented by the formula H 3 C — N — C. Hence it is, in all proba- 
bility, that when they undergo decomposition the nitrogen 
remains in combination with the radical, while the carbon of 
the cyanogen group passes out of the compound. The conduct 
of ethyl isocyanide is represented by the equation : — 

C 2 H 5 .NC + 2H 2 = C 2 H 5 -NH 2 + H.C0 2 H. 

The reactions of the cyanides and of the isocyanides, and 
the conclusions drawn from them, admirably illustrate the 
methods used in determining the structure of compounds of 
carbon ; and they are specially valuable, as the connection 
between the facts and the conclusions, as expressed in the 
formulas, can be traced so clearly. 

The fact, that the silver salt of hydrocyanic acid yields iso- 
cyanides, while the potassium and other salts yield cyanides 
with the halogen derivatives of the hydrocarbons, leads to the 
suspicion that in silver cyanide the metal may be in combina- 
tion with nitrogen and not with carbon. There are other facts 
known which indicate a tendency on the part of silver to unite 
with nitrogen in carbon compounds. It would lead too far to 
discuss this subject here. 

It seems possible that isomeric salts of cyanogen may be dis- 
covered corresponding to the cyanides of the radicals and to the 
isocyanides. There is no fact known which makes the exist- 



90 DERIVATIVES OF METHANE AND ETHANE. 

ence of two. potassium cyanides and two silver cyanides seem 
improbable. The two series of salts would be derivatives 
of hydrocyanic acid, H — C— N, and isohydrocyanic acid, 
H-N-c/ 

Experiment 30. The odor of the isocyanides, as has been stated, 
is extremely disagreeable, and in concentrated form it is unbearable. 
A vivid impression in regard to this property may be produced by the 
following experiment. In a test-tube bring together a little chloroform, 
aniline, and alcoholic potash. The reaction takes place at once. It is 
better to perform the experiment out-of-doors, and in such a place that 
the tube with its contents can be thrown away without molesting any 
one. The aniline used is a substituted ammonia analogous to methyl- 
amine, containing the radical C 6 H 5 in place of methyl. The isocyanide 



Cyanates and Isocyanates. 

There are two series of compounds bearing to cyanic acid 
much the same relation as that which the C3 T anides and isocyan- 
ides bear to hydrocyanic acid. 

In the cyanates, which are made by passing cyanogen chloride 
into the alcoholates (CH 3 ONa+CNCl=CH 3 OCN + NaCl), the 
radical is believed to be united to the cyanogen group by means 
of oxygen, as represented in the formula CH 3 — O — CN. 

In the isocyanates (first called cyanates) , on the other hand, 
the radical is believed to be united to the cyanogen by means 
of nitrogen, as represented thus, CH 3 — N— CO. The isocyan- 
ates are made by distilling potassium cyanate with the potassium 
salt of methyl- or ethyl-sulphuric acid. They can be made also 
by bringing together the iodides of radicals, as iodo-methane 
and silver cyanate. They are very volatile substances, which 
have penetrating and suffocating odors. 

One of the principal reactions of the cyanates is that which 
they undergo with caustic alkalies, hydrochloric acid, etc. They 
yield cyanic acid, and a compound containing the radical which 
they contained. 



ISO-STJLPHO-CYANATES. 91 

The isocj'anates readily yield substituted ammonias, just as 
the isoc}'anides do : — 

C 2 H 5 -N-CO + H 2 = C 2 H 5 .NH 2 + C0 2 ; 
CH 3 -N-CO + H 2 = CH 3 .NH 2 + C0 2 . 

The views held in regard to the structure of the cyauates and 
isocyanates are based upon these reactions, which, as will be 
observed, are very similar to those more fully presented in 
discussing the difference between the cyanides and isocyanides. 

The existence of two cyanic acids, and of two series of salts 
derived from them, seems probable. 

SULPHO-CYANATES. 

The ethereal salts of sulphocyanic acid are easily made by 
distilling potassium sulphocyanate and the potassium salt of 
methyl- or ethyl-sulphuric acid : — 

CH3 >S0 4 -f KSCN = CH 3 SCN + K 2 S0 4 . 
K 

The ethyl compound, which is very similar to the methyl com- 
pound, is a liquid boiling at 146°. 

When boiled with nitric acid, it is oxidized to ethyl-sulphonic 
acid. Now, it has been shown above (see p. 77), that in ethyl- 
sulphonic acid the ethyl in all probability is in combination with 
the sulphur. It hence follows that, in the sulphocyanates 
obtained from potassium sulphocyanate, the radical is also 
in combination with sulphur, as indicated in the formula, 
C 2 H 5 — S — CN. This view is supported by the fact that ethyl 
sulpho-cyanate readily yields ethyl sulphide as a product of 
decomposition. 

ISO-SULPHO-CYANATES OR MuSTARD-OlLS. 

A number of compounds are known isomeric with the sulpho- 
cyanates. The best-known member of the class is ordinary 
mustard-oil. Hence they have been called mustard-oils, and 



92 DERIVATIVES OF METHANE AND ETHANE. 

they are known most frequently by this name. The mustard- 
oils are made by means of a series of somewhat complicated 
reactions, which it is rather difficult to interpret without a com- 
parison with some similar reactions which take place between 
simpler substances. 

When dry ammonia and dry carbon dioxide act upon each 
other, so-called anhydrous ammonium carbonate is formed. This 

TSJTT 

is really the ammonium salt of carbamic acid, CO < OH ' 2 . Its 
formation is represented thus : — 

C0 2 + 2NH s =CO<^. 

Now, remembering that carbon disulphide is similar to carbon 
dioxide, and that ethyl-amine is similar to ammonia, we can 
readily understand the reaction which takes place when these 
two substances are brought together : — 

CS 2 + 2 NH 2 C 2 H 5 = CS < NHC 2 H 5 

2 2 2 5 S(NH 3 C 2 H 5 ) 

The product formed is the ethyl-ammonium salt of the acid 

CS < 2 °, which may be called ethyl-sulpho-carbamic acid. 

SH 

When the ethyl-ammonium salt is treated with silver nitrate, the 

NHC.JL . ....-, A t 

corresponding silver salt, CS < " , is precipitated. And 

finally, when this salt is distilled, it breaks up, yielding ethyl 
mustard-oil ^ silver sulphide, and hydrogen sulphide : — 

2 CS < NHC 2 H 5 = 2 sc _ NaHs + H2 g + A s . 

SAg 

Ethyl mustard-oil is an oily liquid which does not mix with 
water. It has a very penetrating odor, and acts upon the 
mucous membranes of the eyes and nose in the same way as 
ordinary oil of mustard. The properties of the two are so much 
alike that one could be substituted for the other. 



ISO-SULPHO-CYANATES. 93 

Some of the arguments have been stated which lead to the 
view that in the sulpho-cyanates the radical is in combination 
with sulphur. Having once accepted this view, we should 
naturally suspect that in the mustard-oils the radical is in com- 
bination with nitrogen, and the question arises whether the 
reactions of these bodies are of such a character as to justify 
this suspicion? They certainly are. In the first place, when 
heated with water or with hydrochloric acid, ethyl mustard-oil is 
decomposed, yielding ethyl-amine, carbon dioxide, and hydrogen 
sulphide : — 

SC-NC 2 H 5 -f 2 H 2 = C 2 H 5 .NH 2 + H 2 S + C0 2 . 

And, in the second place, nascent hydrogen converts it into 
ethyl-amine and formic thioaldehyde (i.e., formic aldehyde in 
which the oxygen has been replaced by sulphur) : — 

SC-NC 2 H 5 + 4H = C 2 H 5 .NH 2 + H 2 CS. 

Thus, as will be seen, the tendency of the sulpho-cyanates is to 
yield sulphides of the radicals like ethyl sulphide, (C 2 H 5 ) 2 S ; 
the tendene}' of the iso-sulpho-cyanates is to yield substituted 
ammonias, like ethyl-amine NH 2 .C 2 H 5 . These facts point to 
the relations expressed in the formulas, R — S— CN for the 
sulpho-cyanates, and R — N— CS for the iso-sulpho-cyanates or 
mustard-oils. 

In reviewing now the compounds of the hydrocarbons which 
are related to cyanogen, we see that there are two isomeric 
series of these, the names and general formulas of which are 
given below : — 

Cyanides, R—C—N . . . Isocyanides or] -r>^-_p 

Carbamines, j 

Cyanates, R— O — CN . . . Isocyanates, R— N— CO. 

Sulpho-cyanates, R—S — CN . Iso-sulpho-cyan- 
ates or Mus- \ 
tard oils, 



94 DERIVATIVES OF METHANE AND ETHANE. 

Note for Student. — Study these compounds until the exact con- 
nection between the formulas and the facts above stated is clearly 
seen. 

Substituted Ammonias. 

When brom- ethane or any similar substitution-product is 
treated with ammonia, the reactions represented by the follow- 
ing equations take place step by step : — 

C 2 H 5 Br + NH 3 = NH 2 (C 2 H 5 ).HBr ; 

C 2 H 5 Br + NH 2 (C 2 H 5 ) = NH(C 2 H 5 ) 2 .HBr ; 
C 2 H 5 Br + NH(C 2 H 5 ) 2 = N(C 2 H 5 ) 3 .HBr ; 

C 2 H 5 Br + N(C 2 H 5 ) 3 = N(C 2 H 5 ) 4 Br. 

The first three products are salts of hydrobromic acid, and 
substances which in all their properties very closely resemble 
ammonia. When these salts are distilled with potassium 
hydroxide they are decomposed, just as ammonium bromide 
would be. Only instead of getting ammonia and potassium 
bromide, we get the compounds ethyl-am ine, NH 2 .C 2 H 5 , di-ethyl- 
amine, NH(C 2 H 5 ) 2 , and tri-ethyl-amine 1 N(C 2 H 5 ) 3 . These 
substances may be regarded as derived from ammonia by the 
replacement of one, two, and three of the hydrogen atoms 
respectively by ethyl. The last product of the series of reac- 
tions represented above may be regarded as ammonium bromide, 
NH 4 Br, in which all four hydrogen atoms are replaced by ethyl 
groups. 

The decomposition by potassium hydroxide of the first two 
salts is represented thus : — 

NH 2 (C 2 H 5 ).HBr + KOH = NH 2 (C 2 H 5 ) + KBr + H 2 ; 
NH(C 2 H 5 ) 2 .HBr + KOH = NH(C 2 H 5 ) 2 + KBr -f- H 2 0. 

Methyl-amine, NH 2 .CH 3 . — This compound can be pre- 
pared by treating iodo-methane with ammonia : — 

CH 3 I 4- NH 3 = NH 2 CH 3 .HI. 



DI-METHYL-AMINE. 95 

Tt was first made by treating methyl isocyanate, CH 3 — N— CO, 
with caustic potash : — 

CH3-N-CO + H 2 = NH 2 .CH 3 + C0 2 . 

It has been stated that it is formed by treating hydrocyanic 
acid with nascent hydrogen : — 

HCN +4H = NH 2 .CH 3 . 

It occurs in nature in herring brine, in Mercurialis perennis, 
and is one of the products of the distillation of animal matter 
as well as of wood. 

Methyl- amine is a gas which is easily condensed to a liquid. 
It smells like ammonia. It is, like ammonia, extremely easily 
soluble in water, 1 volume of water at 12.5° taking up 1150 
volumes of the gas. This solution acts almost exactly like a 
solution of ammonia in water. It is strongly alkaline. It pre- 
cipitates the metallic hydroxides, but, unlike ammonia, it does 
not redissolve precipitated hydroxides of nickel, cobalt, and 
cadmium when added in excess. Like ammonia, it dissolves 
aluminium hydroxide. 

Methyl- amine forms salts with acids in the same way that 
ammonia does ; that is, by direct addition. The action towards 
nitric and sulphuric acids takes place in accordance with the 
following equations : — 

NH 2 CH 3 + HN0 3 = NH 3 CH 3 .N0 3 ; 
2 NH 2 CH 3 + H 2 S0 4 = (NH 3 CH 3 ) 2 S0 4 . 

These salts are called methyl-ammonium nitrate and methyl- 
ammonium sulphate respectively. 

Di-methyl-amine, NH(CH 3 ) 2 . — This is formed by heating 
iodo-methane with alcoholic ammonia : — 

2 CH 3 I + 2 NH 3 = NH(CH 3 ) 2 .HI + NHJ. 



96 DERIVATIVES OE METHANE AND ETHANE. 

It is formed, together with methyl- amine, as a product of the 
distillation of wood. 

It is a gas which condenses to a liquid at +8°. Its proper- 
ties are much like those of methyl-amine. 

Tri-methyl-amine, N(CH :5 ) 3 . — Tri-methyl-amine is formed 
as one of the products of the treatment of iodo-methane with 
ammonia. It occurs widely distributed in nature, as in the 
blossoms of the hawthorn, the wild cherry, and the pear. It 
is contained in herring brine, and is a common product of the 
decomposition of organic substances which contain nitrogen. It 
is now obtained in large quantities from the so-called ' ' vin- 
asses." These are the waste liquids obtained in the refining of 
beet sugar. When the " vinasses " are evaporated to dryness, 
tri-metlryl-amine is given off among the volatile products. It is 
collected as the hydrochloric acid salt, N(CH 3 ) 3 .HC1, which, 
when heated to 260°, yields ammonia, tri-methyl-amine, and 
chlor-methane : — 

3 N(CH 3 ) 3 .HC1 = 2 N(CH 3 ) 3 + NH 3 + 3 CH 3 C1. 

The chlor-methane is utilized for the purpose of producing low 
temperatures. 

Tri-methyl-amine is a liquid boiling at 9° to 10°. It has a 
strong ammoniacal and fishy odor. It is very soluble in water 
and alcohol, and is a stroug base. Its use in the preparation of 
potassium carbonate, by the Solvay process, has been suggested. 
In making sodium carbonate from the chloride by this method, 
acid ammonium carbonate is added to the chloride. Thus 
mono-sodium carbonate is precipitated, and ammonium chloride 
is left in solution. But mono-potassium carbonate and ammo- 
nium chloride are about equally soluble, so that potassium car- 
bonate cannot be prepared in the same way. On the other 
hand, if tri-methyl-amine is substituted for ammonia, the sepa- 
ration can be effected, inasmuch as tri-methyl-ammonium chlo- 
ride is more soluble than ammonium chloride. 



TKI-METHYL-AMINE* 97 

Note for Student. — Write the equations representing the reac- 
tions involved in making potassium carbonate from potassium chloride 
by means of tri-methyl-amine. 

The ethyl-amines are very much like the methyl compounds, 
and hence need not be specially described. 

When tri-ethyl-amine is brought together with iodo-ethane, 
the two unite, forming the compound tetra-ethyl-ammonium 
iodide, N(C 2 H 5 ) 4 I, which is ammonium iodide, in which all four 
hydrogen atoms have been replaced by ethyl groups. If silver 
oxide is added to the aqueous solution of the iodide, silver 
iodide is precipitated, and by evaporation of the liquid crystals 
of tetra-ethyl-ammonium hydroxide, N(C 2 H 5 ) 4 OH, are obtained. 
This is plainly the hypothetical ammonium hydroxide, in which 
the four ammonium hydrogens have been replaced by ethyl. 
Its solution acts almost like caustic potash. It is very caustic, 
attracts carbon dioxide from the air, saponifies (see p. 70) 
ethereal salts, and gives the same precipitates as caustic potash. 
The reactions of the substituted ammonias above described 
make it certain that these bodies are very closely related to 
ammonia. The methods of formation also point clearl}- to the 
same conclusion. This relation is best expressed by the form- 
ulas above given. 

Another method for the formation of substituted ammonias 
in which but one radical is present, as ethyl-amine, NH 2 .C 2 H 5 , 
or in general NH 2 . R, consists in treating with nascent hydro- 
gen compounds known as niiro compounds, which are substi- 
tution-products containing the group N0 2 in the place of 
lrydrogen. Thus, for example, when nitro-methane, CH 3 . N0 2 
(which see), is treated with hydrogen, the reaction which takes 
place is represented thus : — 

CH 3 .N0 2 -f 6 H = CH 3 .NH 2 + 2 H 2 0. 

In connection with another series, it will be shown that this 
reaction is a most important one, from a practical as well as 
a scientific point of view. It may be said in anticipation that 



98 DERIVATIVES OF METHANE AND ETHANE. 

the manufacture of aniline, and consequently of all the many 
valuable dye-stuffs related to aniline, is based upon this reac- 
tion. 

Just as we may look upon methyl-amine and the related com- 
pounds, as ammonia, in which one hydrogen atom is replaced by 
methyl, so also we may regard them, and with equal right, as 
marsh gas, in which hydrogen has been replaced by the group or 
residue NH 2 . Owing to the frequency of the occurrence of this 
group in carbon compounds, and for the sake of simplifying the 
nomenclature, the group has been called the amide or amido 
group, and the bodies containing it amido -compounds. Thus 
the compound NH 2 . C 2 H 5 may be called either ethyl-amine or 
amido -ethane, etc. 

Similarly, those bodies which contain two hydrocarbon resi- 
dues, as di-ethyl-amine, NH(C 2 H 5 ) 2 , are called imido-compounds, 
and the group NH the imide or imido group. Substituted 
ammonias containing one hydrocarbon residue are called pri- 
mary ammonia bases. Those containing two residues, as di- 
ethyl-amine, NH(C 2 H 5 ) 2 , are known as secondary ammonia 
bases, and those containing three residues, as tri-ethyl-amine, 
N(CH 3 ) S , are called tertiary ammonia bases. 

Among the most important of the reactions of amido-com- 
pounds or primary bases is that which takes place when they 
are treated with nitrous acid. Take ethyl-amine as an illustra- 
tion. In order to understand what takes place when this 
compound is treated with nitrous, acid, it is necessary to keep 
in mind the fact that the compound itself is a modified ammo- 
nia, and hence we may expect that its reactions will be but 
modifications of those which take place with ammonia. Thus 
with nitrous acid ammonia unites directly to form ammonium 
nitrite : — 

NH 3 + HN0 2 = NH 4 .N0 2 . 

So also ethyl-amine forms ethyl-ammonium nitrite : — 

NH 2 .C 2 H 5 + HN0 2 = NH 3 (C 2 H 5 ).N0 2 . 



NITKO-COMPOTTNDS. 99 

Now we know that ammonium nitrite breaks up readily into 
free nitrogen and water : — 

NH 4 .N0 2 = N 2 + H 2 + H 2 0. 

So also ethyl-ammonium nitrite breaks up into free nitrogen, 
water, and alcohol : — 

NH 3 (C 2 H 5 )N0 2 = N 2 + H 2 + C 2 H 5 .OH. 

The two reactions are strictly analogous. As in the second case 
we start with a substituted ammonia, we get as a product a 
substituted water or alcohol. 

This reaction has been used very extensively in the prepara- 
tion of bodies containing hydroxyl. For ordinary alcohol, as 
is clear, it is not a convenient method of preparation ; but it 
will be shown that there are hydroxides for the preparation of 
which it is by far the most convenient method. The essential 
character of the transformation effected by it will be best under- 
stood by comparing the formulas of the amide and the alcohol. 
We have ethyl-amine, C 2 H 5 . NH 2 , and from it we get alcohol, 
C 2 H 5 . OH. Thus we see that the transformation consists in 
replacing the amido-group by hydroxyl. 

Hydrazine Compounds. 

There is an important class of compounds, the members of 
which bear the same relation to the compound hydrazine, N 2 H 4 
(H 2 N — NH 2 ), that the substituted ammonias bear to ammonia. 
The reactions by which they are prepared are somewhat com- 
plicated, and cannot well be discussed at this stage. The best- 
known hydrazines are those related to the hydrocarbons of the 
benzene series, as, for example, phenylhydrazine, C 6 H 5 .NH.NH 2 . 

NlTRO-COMPOUNDS. 

Reference has already been made to a class of bodies con- 
taining the group N0 2 , and known as nitro-compounds. They 
are most readily made b}^ treating the hydrocarbons with nitric 



100 DERIVATIVES OE METHANE AND ETHANE. 

acid. This method, however, is not applicable to the hydro- 
carbons methane and ethane and their homologues, as these can 
be treated with nitric acid without undergoing change. The 
hydrocarbon benzene, C 6 H 6 , is acted upon very easily by nitric 
acid, when the reaction represented by the following equation 
takes place : — 

C 6 H 6 + HO.N0 2 = C 6 H 5 .N0 2 + H 2 0. 

The action is like that which takes place between sulphuric 
acid and benzene, which gives the sulphonic acid C 6 H 5 .S0 2 OH 

C* IT 

or JL 5 > S0 2- (Seep. 76.) In each case a hydrox}! of the 
HO 

acid is replaced by the simple residue of the hydrocarbon. The 
product in the case of the dibasic acid, sulphuric acid, is itself 
still acid, while the product in the case of the monobasic nitric 
acid, is not an acid. 

The nitro-derivatives of methane have been made by a reac- 
tion which we should expect to yield ethereal salts of nitrous 
acid ; namely, by treating iodo-methane or ethane with silver 
nitrite : — 

CH 3 I + AgN0 2 '= CH 3 N0 2 + Agl. 

The compound CH 3 .NO a , which is known as nitro-methane, 
does not conduct itself like the ethereal salts of nitrous acid. 
The latter are unstable bodies, while the former is stable. 

Note for Student. — Compare the reaction just referred to with 
that which takes place between silver cyanide and iodo-methane ; and 
that which takes place between iodo-ethane and potassium sulphite. 
What analogy is there to the former and to the latter? 

It has already been stated that the nitro-derivatives are con- 
verted b}^ nascent hydrogen into the corresponding amido- 
derivatives (see p. 97). 

Note for Student. — Write the equations representing the reac- 
tions necessary to convert methyl alcohol into methyl-amine by means 
of the nitro-compound. 



NITROSO- AND ISONITROSO-COMPOUNDS. 101 

Nitroform, CH(N0 2 ) 3 , as the formula indicates, is the tri- 
nitro-derivative of methane, or tri-nitro-methane. It is con- 
verted into tetra-nitro-methane, C(N0 2 ) 4 , when treated with a 
mixture of concentrated sulphuric and fuming nitric acids. 

Nitro-chloroform, C(N0 2 )C1 3 , called also chlorpicrin and 
nitro-trichlormethane, is formed by distilling methyl or ethy] 
alcohol with common salt, saltpetre, and sulphuric acid. It is 
formed from a number of more complicated nitro-compounds, 
by distilling them with bleaching lime or hydrochloric acid and 
potassium chlorate. 

NlTROSO- AND ISONITROSO-COMPOUNDS, 

When a compound containing the group CH is treated with 
nitrous a acid, a reaction takes place, which is represented thus : — 

R 3 .CH + HO. NO = R3.C.NO + H 2 0. 

The product R 3 .C.NO, which is derived from the original sub- 
stance by the substitution of the group NO for a hydrogen 
atom, is called a nitro so-compound. By oxidation the nitroso- 
compounds are converted into nitro-compounds, and by reduc- 
tion they yield the same products as the corresponding nitro- 
compounds. 

The isonitroso-compounds are isomeric with the nitroso-com- 
pounds. They are formed when acetones or aldehydes are 
treated with hydroxylamine, NH 2 .OH. The reaction may be 
represented thus : — 

CH3 ^Hs 

I I 

CO + H 2 N.OH = C-N-OH + H 2 0. 

I I 

CH 3 CH 3 

The hydrogen of the hydroxy 1 has acid properties. The 
isonitroso-compounds are readily broken up, yielding, as one 
of the products, hydroxylamine. They are generally called 
oximes,. 



102 DERIVATIVES OF METHANE AND ETHANE. 

Fulminic acid, C 2 N 2 2 H 2 , according to recent investiga* 
tions, appears to be an isonitroso-compound, and tor that 
reason finds appropriate mention in this place. The principal 
compound of fulminic acid, is the mercury salt, C 2 N 2 2 Hg, 
commonly known as fulminating mercury. It is prepared by 
dissolving mercury in strong nitric acid, and adding alcohol to 
the solution. It is extremely explosive. Mixed with potassium 
nitrate it is used for filling percussion-caps. 

When fulminating mercury is treated with concentrated hydro- 
chloric acid, it yields hydroxylamine as one of the products of 
decomposition. This is regarded as evidence that fulminic acid 
is an isonitroso-compound. As will be seen, fulminic acid is 
isomeric with cyanic and cyanuric acids (see pp. 83 and 84). 



CHAPTER VII. 

DERIVATIVES OP METHANE AND ETHANE CON- 
TAINING PHOSPHORUS, ARSENIC, ETC. 

Phosphorus compounds.— Corresponding to the amines or 
substituted ammonias are the phosphines, which, as the name 
implies, are related to phosphine, PH 3 . Methyl-phosphine, 
PH 2 .CH 3 , di-methyl-phosphine, PH(CH 3 ) 2 , and tri-methyl- 
phosphine, P(CH 3 ) 3 , may be taken as examples. 

These substances, like the corresponding amines, form salts 
with acids, though not as readily. The hydroxide, tetra-ethyl- 
phosplwnium hydroxide, P(C 2 H 5 ) 4 .OH, is a very strong base, 
though not as strong as the corresponding nitrogen derivative. 

The phosphines have one marked property which distin- 
guishes them from the amines, and that is their power to take 
up oxygen and form acids, Thus, ethyl-phosphine, PH 2 .C 2 H 5 , 
when treated with nitric acid, is converted into etliyl-plios- 
p7iinic acid, PO(C 2 H 5 ) (OH) 2 , a dibasic acid, bearing to phos- 
phoric acid the same relation that the sulphonic acids bear to 
sulphuric acid. 

Note for Student. — What is the relation? What other class of 
acids bears the same relation to carbonic acid? 

Di-ethyl-phosphine, PH(C 2 H 5 ) 2 , yields di-ethyl-pliosplunic acid, 
PO(C 2 H 5 ) 2 .OH, when oxidized. 

These compounds are not commonly met with, and do not 
play a very important part in the stud}' of the compounds of 
carbon. 

Arsenic compounds. — The most characteristic carbon 
compound containing arsenic is that which is known as cacc 



104 DERIVATIVES OF METHANE AND ETHANE. 

a name given to it on account of its extremely disagreeable 
odor (from koikojS^?, stinking) . It is prepared by distilling a mix- 
ture of potassium acetate and arsenic trioxide. The reactions 
which take place are very complicated, and many products are 
formed. Chief among the products is cacodyl oxide : — 

4CH 3 .C0 2 K + As 2 3 = [(CH 3 ) 2 As] 2 + 2 K 2 C0 3 + 2 C0 2 . 

When treated with hydrochloric acid, the oxide is converted 
into the chloride (CH 3 ) 2 AsCl ; and, when the chloride is treated 
with zinc, cacodyl itself is produced. Its analysis and the 
determination of its molecular weight lead to the formula 
As 2 C 4 Hi2, which in all probability should be represented thus : 

32 s I . Cacodyl appears thus as a compound analogous 

(v_/Hg) 9 As ) 

to the hydrazines referred to above. (See p. 99.) 
Note for Student. — In what does the analogy consist? 

Many derivatives of cacodyl have been made, but their study 
would hardly be profitable at this stage. 

By treating the chlorides of silicon, boron, and many of the 
metals with zinc ethyl, Zn(C 2 H 5 ) 2 , many similar ethyl deriva- 
tives have been made. 

Zinc ethyl itself is made by treating iodo-ethane, C 2 H 5 I, 
with zinc alone or with zinc sodium : — 

ZnNa 2 + 2 C 2 H 5 I = Zn(C 2 H 5 ) 2 + 2 Nal. 

It is a liquid boiling at 118°. It takes fire in the air, and burns 
with a white flame. 

Sodium-ethyl, C 2 H 5 Na, can be obtained in combination 
with zinc ethyl by treating the latter with sodium. Both these 
compounds have been used to a considerable extent in the syn- 
thesis of carbon compounds, particularly the more complex 
hydrocarbons, and they will be frequently referred to in the 
following pages. 



RETROSPECT. 105 

Note for Student. — What is formed when sodium methjd and 
carbon dioxide are allowed to act upon each other? 

Many of the derivatives, like the above, are volatile liquids. 
Such, for example, are mercury ethyl, Hg(C 2 H 3 ) 2 , aluminium 
ethyl, A1(C 2 H 5 ) 3 , tin tetrethyl, Sn(C 2 H 5 ) 4 , and silicon tetrethyl, 
Si(C 2 H 5 ) 4 . The study of these compounds has been of assist- 
ance in enabling chemists to determine the atomic weights of 
some of the elements which do not form simple volatile 
compounds. 

Retrospect. 

In the introductory chapter (p. 19) these words were used in 
describing the plan to be followed: "Of the first series of 
lryclrocarbons two members will be considered. Then the de- 
rivatives of these two will be taken up. These derivatives will 
serve admirably as representatives of the corresponding deriva- 
tives of other hydrocarbons of the same series and of other 
series. Their characteristics and then relations to the hydro- 
carbons will be dwelt upon, as well as their relations to each 
other. Thus, by a comparativeby close study of two hydro- 
carbons and their derivatives, we may acquire a knowledge of 
the principal classes of the compounds of carbon. After these 
typical derivatives have been considered, the entire series of 
hydrocarbons will be taken up briefly, only such facts being 
dealt with at all fully as are not illustrated by the first two 
members." 

In accordance with the plan thus sketched we have thus far 
studied the principal derivatives of the two hydrocarbons, 
methane and ethane, so far as these derivatives represent dis- 
tinct classes of compounds. These derivatives were classified 
first into (1) those containing halogens; (2) those containing 
oxygen ; (3) those containing sulphur ; aud (4) those contain- 
ing nitrogen. On examining each of these classes more closely, 
we found that the halogen derivatives, such as chlor-methane, 
brom-ethane, etc., bear very simple relations to each other. 



106 DERIVATIVES OF METHANE AND ETHANE. 

We found that under the head of oxygen derivatives, the most 
important and most distinctly characteristic derivatives of 
hydro-carbons are met with ; as, the alcohols, ethers, aldehydes, 
acids, ethereal salts, and ketones. The sulphur derivatives, 
some of which closely resemble the oxygen derivatives, include 
the sulphur alcohols or mercaptans, sulphur ethers, and sulphonic 
acids. 

On beginning the consideration of the nitrogen derivatives 
we found it desirable first to take up certain derivatives con- 
taining the cyanogen group, among which are cyanogen, hydro- 
cyanic acid, cyanic acid, and sulphocyanic acid. Many interest- 
ing carbon compounds are closely related to these fundamental 
compounds. Such, for example, are the cyanides and carba- 
mines, the cyanates and isocyanates, the sulpho-cyanates and 
iso-sulpho-cyanates or mustard-oils. Following the compounds 
related to cyanogen, we took up the interesting compounds 
which are related to ammonia, the substituted ammonias or 
amines. Then came the nitro-derivatives ; and, finally, the 
compounds of the hydrocarbon residues or radicals with metals. 

It is of the greatest importance that the student should 
master the preceding portion of this book. If he studies care- 
fully the reactions which have been considered, and which are 
statements in chemical language which tell us the conduct of 
the various classes of derivatives, and if he performs the ex- 
periments which have been described, he will have a fair general 
knowledge of the kinds of relations which are met with in con- 
nection with the compounds of carbon through the whole field. 
As stated in the Introduction : " If we know what derivatives 
one hydrocarbon can yield, we know what derivatives we may 
expect to find in the case of every other hydrocarbon." 

The more the student practises the use of the equations thus 
far given, the better he will be prepared to follow the remain- 
ing portions of the book. Indeed, it may be said that, if he 
thoroughly understands what has gone before, what follows will 
appear extremely simple. Whereas, if he has failed at an^ 



RETROSPECT. 107 

point to catch the exact meaning, if he has failed to see the 
connection, he had better go back and faithfully review, or he 
will soon find his mind hopelessly muddled, and relations which 
are as clear as day will be concealed from him. 

A very excellent practice is to trace connections between the 
different classes of compounds, and show how to pass from one 
to the other. Thus, for example, (1) show by what reactions 
it is possible to pass from marsh gas to acetic acid. (2) How 
can we pass from ordinary alcohol to ethylidene chloride, 
CH 3 .CHC1 2 ? (3) What reactions would enable us to make 
methyl-amine from its elements? (4) How can acetone be 
made from methyl-amine ? (5) What reactions are necessary in 
order to make ordinary ether from ethyl-amine? etc., etc. It 
is well in this sort of practice to select what appear to be the 
least closely -related compounds, and to show then how we can 
pass from one to the other. Be sure to select representatives 
of all the classes hitherto mentioned, and to bring in all the 
important reactions. 



CHAPTER VIII. 

THE HYDROCARBONS OP THE MARSH-GAS 
SERIES, OR PARAFFINS. 

The existence of the homologous series of Irydrocarbons be- 
ginning with methane and ethane was spoken of before its first 
two members were considered. A general idea of the extent 
of the series, and of the names used to designate the members, 
may be gained from the following table : — 



MARSH-GAS HYDROCARBONS. 


Paraffins. — Hydrocarbons, 


-^nH 2n + 2 . 




Boiling-Point 


Methane .... CH 4 


. .- gas. 


Ethane . 
Propane 






• C 2 H 6 
. C 3 H 8 


. . gas. 
. . gas. 


Butane . 
Pentane 
Hexane 






• C 4 H 10 . 

• QH 12 • 

• C 6 H U . 


. . 1°. 

. 38°. 
. 70°. 


Heptane 
Octane . 






• C 7 H 16 . . 
C 8 H 18 . 


. 98.4°. 
. 125°. 


Nonane 






C 9 H 20 


. 148°. 


Dodecane . 






C ]2 H 26 . 


. 202°. 


Hecdecane 






C 16 H34 . 


. 278°. 



The explanation of the remarkable relation in composition 
existing between these members, a relation to which the name 
homology is given, has already been referred to (p. 22). The 
number of hydrogen atoms contained in a member of this series 



PETROLEUM. 109 

bears a constant relation to the number of carbon atoms, as 
expressed in the general formula C n H 2n+2 . On examining the 
column headed " Boiling-Point " it will be seen that, as we pass 
upward in the series, the boiling-point becomes higher and higher. 
The first three members are gases at ordinary temperatures, while 
the last boils at 278°. The elevation in the boiling-point is 
to some extent regular, as will be observed. The difference 
between butane. C 4 H 10 , and pentane, C 5 H 12 , is 38 — 1 = 37° ; 
that between pentane and the next member is 70 — 38 = 32° ; 
between hexane and heptane it is 98.4 — 70 = 28.4° ; between 
heptane and octane, 125 — 98.4 = 26.6° ; and, finally, between 
octane and nonane the difference is 148 — 125 = 23°. Thus it 
will be seen that the elevation in boiling-point caused by the 
addition of CH 2 decreases as we pass upward in the series. 
Other relations have been pointed out, but it would be prema- 
ture to discuss them here. 

The chief natural source of the paraffins is petroleum ; but 
although this substance, which occurs in such enormous quanti- 
ties in nature, undoubtedly contains a number of the members 
of the paraffin series, it is an extremely difficult matter to 
isolate them from the mixture. Prolonged fractional distilla- 
tion is not sufficient for the purpose. If, however, some of the 
purest products which can thus be obtained are treated with 
concentrated sulphuric acid, and afterwards with concentrated 
nitric acid, and then washed and redistilled, they can be 
obtained in pure condition. 

Petroleum. — Petroleum occurs in enormous quantities in 
several places. Among the most important localities are 
Pennsylvania, the Crimea, the Caucasus, Persia, Burmah, 
China, etc. In some places it issues constantly from the 
earth. Usually it is necessary to bore for it. When one of 
the cavities in which it is contained is punctured, the oil 
is forced out of a pipe inserted into the opening in a jet, in 
consequence of the pressure exerted upon its surface. As 



110 HYDROCARBONS OF THE MARSH-GAS SERIES. 

first obtained, it is usually a dark, 3 T ellowish-greeu liquid, with 
au unpleasant odor. It varies in appearance according to the 
place in which it is found. American petroleum contains the 
lowest members of the paraffin series ; and when the oil is 
exposed to the air the gases are given off. 

Refining of petroleum. To render petroleum fit for use in 
lamps, it is necessary that the volatile portions should be 
removed, as the}" form explosive mixtures with air, just as 
marsh gas does. It is also necessary to remove the higher 
boiling portions, because they are semi-solid, and would clog 
the wicks of the lamps. The crude oil is therefore subjected to 
distillation, and only those parts which have a certain specific 
gravity or boil between certain points are used for illuminating 
purposes, under the name of kerosene. Besides being distilled, 
the oil must further be treated with concentrated sulphuric 
acid, which removes a number of undesirable substances, and 
afterwards with an alkali, and then with water. All these 
processes taken together constitute what is called the refining 
of petroleum. In the distillation, the lighter products are 
usually divided into several parts, according to the specific 
gravity or boiling-point. Thus we have the products cymogene, 
rhigolene, gasoline, naphtha, and benzine, all of which are 
lighter than kerosene. It must be distinctly understood that 
the substances here mentioned are not pure chemical indi- 
viduals. The names are commercial names, each of which 
applies to a complex mixture of hydrocarbons. From the 
heavier products, that is, those that boil at higher tempera- 
tures than the highest limit for kerosene, paraffin, which is a 
mixture of the highest members of this series, is made. 

Owing to the danger attendant upon the use of improperly 
refined petroleum, laws have been enacted relating to the 
properties which the kerosene exposed for sale must have. 
These laws, which differ somewhat in different countries and 
different parts of the same country, relate mostly to what is 
called the flashing -point. This is the temperature to which the 



SYNTHESIS OF THE PARAFFINS. 



Ill 



oil must be heated before it takes fire when a flame is applied 
to it. The legal flashing-point in many parts of the United 
States is 44°. A simple and accurate instrument for deter- 
mining the flashing-point is here' described : The cylinder A 
is at least 2.5 cm in diameter, and at least 16 cm long. Just 
within the cork the bent tube contracts 
to a small orifice. At d it is connected 
with a hand-bellows or a gas-holder ; and 
the flow of air is controlled by a pinch- 
cock. The cylinder is filled with oil to 
a point such that, when the air is run- 
ning, the surface of the foam is about 
5 cm from the top ; and it is then put 
in a water- bath to the level of the oil. 
Air is now passed through deb, and e so 
adjusted that about 0.5 cm foam is kept 
on the surface of the oil. From degree to degree the test is 
made by bringing a small flame for an instant to the mouth of 
A. At the flashing-point the vapor ignites, and the bluish flame 
runs down to the surface of the oil. 




Experiment 31. Make an apparatus like the above, and determine 
the flashing-points of two or three specimens of kerosene that may be 
available. 

Synthesis of the paraffins. — Although the paraffins occur 
in nature, and a few of them can be obtained in pure condition 
from natural sources, we are dependent upon synthetical oper- 
ations performed in the laboratory for our knowledge of the 
series and the relations existing between them. 

We have already seen how ethane can be prepared from 
methane by treating methyl iodide with zinc or sodium, as 
represented in this equation : — 



CH 3 I + CH3I + 2 Na = C 2 H 6 + 2 NaT. 



112 HYDROCARBONS OE THE MARSH-GAS SERIES. 

This method has been extensively used in the building up of 
higher members of the series. Thus from ethane we can make 
ethyl iodide, and by treating this with sodium get butane 
C 4 H ]0 : — 

C 2 H 5 I -f C 2 H 5 I + 2Na = C 4 H 10 + 2 NaT 

But we can get the intermediate member, propane, C 3 H 8 , by 
mixing methyl iodide and ethyl iodide and treating the mixture 
with sodium : — 

CH 3 I + C 2 H 5 I + 2Na = CH 3 .C,H 5 + 2 Nal. 

By applying this method, it is plain that a large number of the 
members of the paraffin series might be made. 

Another method consists in treating the zinc compounds of 
the radicals, like zinc ethyl, Zn(C 2 H 5 ),, with the iodides of rad- 
icals. Thus zinc methyl and methyl iodide give ethane ; zinc 
ethyl and ethyl iodide give butane ; zinc ethyl and methyl 
iodide give propane, etc. : — 

Zn(CH 3 ) 2 + 2CH3I = 2C 2 H 6 + Znl 2 
Zn(C 2 H 5 ) 2 + 2 C 2 H 5 I = 2 C 4 H 10 + Znl 2 
Zn(C 2 H 5 ) 2 + 2 CH3I = 2 C 3 H 8 + Znl 2 . 

Paraffins can be made b} T replacing the halogen in a substitu- 
tion-product by hydrogen. This can be effected by nascent 
hydrogen or by hydriodic acid : — 

C 4 H 9 I + 2 H = C 4 H 10 + HI. 

Finally, the paraffins can be made by heating the acids of the 
formic acid series with an alkali. This has been illustrated by 
the preparation of marsh gas from acetic acid by heating with 
lime and caustic potash. The reaction may be written thus : — 

CH 3 .C0 2 K -f- KOH = CH 4 4- C0 3 K 2 . 

The products are a hydrocarbon and a carbonate. 



1*1 

i 2 ; 



ISOMERISM AMONG THE PARAFFINS. 113 

Isomerism among the paraffins. — It has already been 
stated that the evidence is almost conclusive that each of the 
four hydrogen atoms of marsh gas bears the same relation to the 
carbon, and hence we believe that, as regards the nature cf the 
product, it makes no difference which hydrogen atom is replaced 
by a given atom or radical. According to this, as ethane is the 
methyl derivative of marsh gas, it makes no difference which of 
the hydrogen atoms of marsh gas is replaced b} T the metlryl, the 
product must always be the same, or there is but one ethane 

possible according to the theory. This is represented by the 
H H 
I I 
formula, H — C — C — H, or H 3 C — CH 3 . In ethane, as well as in 
I I 
H H 
methane, all the hydrogen atoms bear the same relation to 
the molecule, and it should make no difference which one is 
replaced by methyl. But propane is regarded as derived from 
ethane by the substitution of methyl for hydrogen ; and, as it 
makes no difference which hydrogen is replaced, there is but 
one propane possible. Only one has ever been discovered, and 
this must be represented thus : — 
H H H 
I I I 
H - C - C - C - H, or CH 3 .CH 2 .CH 3 . 
I I I 
H H H 
Now, continuing the process of substitution of methyl for hydro- 
gen, it appears that the theory indicates the possibilnrv of the 
existence of two compounds of the formula C 4 H 10 . One of 
these should be obtained b}' replacing by methyl one of the three 
hydrogens of either methyl group of propane. It is represented 
by the formula : — 

H H H H 

I 1 I I 

H-C-C-C-C-H, or H 3 C.CH,.CH 2 .CH 3 . 

I I I I 

H H H H 



114 HYDROCARBONS OF THE MARSH-GAS SERIES. 

The other should be obtained by replacing by methyl one of the 
two hydrogens of the group CH 2 contained in propane. This 
would give a hydrocarbon of the formula : — 

H H H CH 3 

III I 

H - C - C - C - H, or CH 3 - CH - CH 3 . 
I I I 

H C H 



H H H 

The theory then indicates the existence of two butanes. How 
about the facts? Two, and only two butanes have been discov- 
ered. The first, which occurs in American petroleum, has been 
made sjnthetically by treating ethyl iodide with zinc : — 

2CH 3 .CH 2 I + Zn = CH 3 .CH 2 .CH 2 .CH 3 + Znl 2 . 

The method of synthesis clearly shows which of the two possi- 
ble isomerides the product is. It is known as normal butane. 
It is a gas which can be condensed to a liquid at +1°. 

The second, or isobutane, is made from an alcohol which 
will be shown to have the structure represented by the formula 
CH 3 

CH 3 — C — OH (see Tertiary Butyl Alcohol, p. 124) , by replacing 

CH 3 
the hydroxyl by hydrogen. It is a gas which becomes liquid 
at -17°. 

The differences between the two butanes are observed princi- 
pally in their derivatives. 

Applying the same method of consideration to the next 
member of the series, how many isomeric varieties of pentane, 
CjHjs, may we expect to find ? The question resolves itself into 
a determination of the number of kinds of hydrogen atoms con- 
tained in the two butanes, or the number of relations to the 
molecule represented among the hydrogen atoms of the butanes. 



PENTANES. 115 

"We can make this determination best by examining the struc- 
tural formulas. Take first normal butane : — 

H H H H 

I I I I 

H-C-C-C-C-H. 

I I I I 

H H H H 

•In this there are plainly two different relations represented ; 
viz., that of each of the six hydrogens in the two methyl groups, 
and that of each of the four hydrogens of the two CH 2 groups. 
The two possible methyl derivatives of a hydrocarbon of this 
formula are therefore to be represented thus : — 

H3O .GH2 .CH2 .C-H^.CELj} (1) 

and H 3 C.CH 2 .CH<^ 3 . (2) 

CH 3 

I 
Now, taking isobutane, HC — CH 3 , we see that it consists of 

I 

CH 3 
three methyl groups, giving nine hydrogen atoms of the same 
kind, and one CH group, the hydrogen of which bears a dif- 
ferent relation to the molecule from that which the other nine 
do. There are therefore two possible methyl derivatives of 
isobutane which must be represented thus : — 

CH 3 CH 3 

I I 

HC - CH 2 .CH 3 (3), and H 3 C - C - CH 3 . (4) 

I I 

CH 3 CH 3 

We have, therefore, apparently four pentanes. But on compar- 
ing formulas (2) and (3), it will be seen that, though written a 
little differently, they really represent one and the same com- 
pound. Thus the number of pentanes, the existence of which 
is indicated by the theory, is three, and these are represented 



116 HYDROCARBONS OF THE MARSH-GAS SERIES. 

by formulas (1), (2), and (4). They are all known. The 
first is called normal pentane, the second iso-pentane or 
di-methyl-ethyl-methane, and the third tetra-methyl-me- 
thane. 

It would lead too far to discuss all the methods of prepara- 
tion and the properties of these hydrocarbons. It will be seen 
that the methods of preparation show what the structure of a 
lrydrocarbon is. Di-mettryl-ethyl-methane is made from an 
alcohol which can be shown to have the formula 

™ 3 >CH.CH 2 .CH 2 OH, 

by replacing the hydroxyl by hydrogen. Hence its structure is 
that represented above by formulas (2) and (3). 

Tetra-methyl-methane is made by starting with acetone. 
Acetone has been shown to consist of carbonyl in combina- 
tion with two methyl groups, as represented in the formula 
CH 3 — CO— CH 3 . It has also been shown that, by treating 
acetone with phosphorus pentachloride, the oxygen is replaced 
by chlorine, giving a compound of the formula CH 3 — CC1 2 — CH 3 . 
Now, by treating this chloride with zinc-methyl, the chlorine is 
replaced by methyl thus : — 

CH 3 
I 
CH 3 -CC1 2 -CH 3 + Zn(CH 3 ) 2 = CH 3 -C-CH 3 + ZnCl 2 . 

I 
CH 3 

The product is tetra-methyl-methane, and the synthesis thus 
effected shows at once what the structure of the product is. 

Hexanes. — The student will now be prepared to apply the 
theory to the determination of the number of hexanes possible. 
He will find that there are five. The theory is, in this case as in 
the preceding, in perfect accordance with the facts. There are 
five and only five hexanes known. Only the names and formu- 
las of these will be given here : — 



HEXANES. 11' 



1. Normal hexane, CH 3 .CH 2 .CH 2 .CH 2 .CH 2 .CH 3 . 

CHc 
CH 3 



2. Iso-hexane, CH 3 .CH 2 .CH 2 .CH < C 



3. Methyl-di-ethyl-methane, CH 3 .CH< CH 2 CH 3 # 

3 CH 2 .CH 3 

4. Tetra-methyl-ethane, ^>HC-CH<^ 3 . 

H 3 G CH 3 

CH 3 
I 

5. Tri-methyl-ethyl-methane, H 3 C-C-CH 2 .CH 3 . 

I 
CH 3 

Passing upward, we find that nine heptanes are possible 
according to the theory, while but five have thus far been 
discovered ; and that, while theory indicates the possibility of 
the discovery of eighteen hydrocarbons of the formula C 8 H 18 , but 
two are known. The theoretical number of isomeric varieties 
of the highest members of the series is very great, but our 
knowledge in regard to these highest members is very limited, 
and it is impossible to say whether the theor}' will ever be 
confirmed by facts. It may be that there is some law limiting 
the number of complicated hydrocarbons. It is, however, idle 
to speculate upon the subject at present. It is well for us to 
keep in mind that a thorough knowledge of a few of the simplest 
members of the series is all that is necessary for the present. 

On examining the formulas used to express the structure of 
the hydrocarbons, we find that they can be divided into three 
classes : — 

(1) Those in which there is no carbon atom in combination 
with more than two others ; as, — 

Propane .... CH 3 .CH 2 .CH 3 ; 
Normal butane . . CH 3 .CH 2 .CH 2 .CH 3 ; 
Normal pentane . CH 3 .CH 2 .CH 2 .CH 2 .CH 3 ; 
and Normal hexane . . CH 3 .CH 2 .CH 2 .CH 2 .CH 2 .CH 3 . 



118 HYDROCARBONS OF THE MARSH-GAS SERIES. 

(2) Those in which there is at least one carbon atom in 
combination with three others; as, — 

Isobutane . . . .CH 3 .CH< CH3 ; 

CH 3 

Isopentane . . . CH 3 .CH 2 .CH< ^ Hs ; 

CH 3 

Isohexane . . . . CH 3 .CH 2 .CH 2 .CH < ^ ; 

CH 3 

and Tetra-methyl-ethane, H ^ > CH - CH < CHs . 

H 3 CH 3 

(3) Those in which there is at least one carbon atom in 
combination with four others; as, — 



Tetra-methyl- 
methane 



}•• 



CH 3 

I 
CH 3 — C — CH 3 ; 

I 
CH 3 

CH, 



, Tri- methyl-ethyl-) ' „ 

and methane } > C 2 H 5 -C-CH 3 . 

CH 3 

The members of the first class are called normal paraffins; 
those of the second class, iso-paraffins ; and those of the third 
class, neo-paraffins. 

Only the members of the same class are strictly comparable 
with each other. Thus it has been found that the boiling-points 
of the normal hydrocarbons bear simple relations to each other, 
and that the same is true of the iso-paraffins ; but, on compar- 
ing the boiling-points and other physical properties of normal 
paraffins with those of the iso- or neo-paraffins, no such simple 
relations are observed. « 



NOMENCLATURE. 119 

Regarding the names of the paraffins, the simplest nomen- 
clature in use is that according to which the hydrocarbons are 
all regarded as derivatives of methane. Thus we get the 

r c 2 h 5 

j TT 

name ethyl-methane for propane, C -j „ ; tri-methyl-methane 



H 
CH 3 [ H r CH 3 

for isobutane, C ^j r 3 ; tetra-methyl- me thane, C •{ p 3 , etc. 



», c] 



CH, 



CHAPTER IX. 

OXYGEN DERIVATIVES OF THE HIGHER MEM- 
BERS OP THE PARAFFIN SERIES. 

We are now to take up the derivatives of the higher mem- 
bers of the paraffin series, just as we took up the derivatives of 
methane and ethane. Not much need be said in regard to the 
halogen derivatives. A few of them will be mentioned in con- 
nection with the corresponding alcohols. The chief substances 
which will require attention are the alcohols and acids. 

1. Alcohols. 

Normal propyl alcohol, CjH 7 .OH. — When sugar under- 
goes fermentation, a little propyl alcohol is always formed, and 
is contained in the " fusel oil." From this it can be separated 
by treating those portions which boil between 85° and 110° 
with phosphorus and bromine. The bromides of the alcohols 
present are thus formed (what is the reaction ?) , and these are 
separated by fractional distillation. The bromide correspond- 
ing to propyl alcohol is then converted into the alcohol (how 
can this be done ?) . 

It is a colorless liquid with a pleasant odor. It boils at 97.4° 
(compare with the boiling-points of methyl and ethyl alcohol) . 
It conducts itself almost exactly like the first two members of 
the series. By oxidation it is converted into an aldehyde, 
C 3 H 6 0, and an acid, C 3 H 6 2 , which bear to it the same relations 
that acetic aldehyde and acetic acid bear to ethyl alcohol. 

Secondary propyl or isopropyl alcohol, C 3 H 7 .OH. — 
The reasons for regarding the alcohols as hydroxyl derivatives 



SECONDARY ALCOHOLS. 121 

of the hydrocarbons have been given pretty fully. As the six 
hydrogen atoms of ethane are all of the same kind, but one 
ethyl alcohol appears to be possible and only one is known. 
But just as there are two butanes or methyl derivatives of pro- 
pane, so there are two hydroxyl derivatives of propane ; or, in 
other words, two propyl alcohols. The first is the one obtained 
from " fusel oil," the other is the one called secondary propyl 
alcohol. This has already been referred to under the head of 
Acetone (see p. 72), where it was stated that acetone is con- 
verted into secondary propyl alcohol by nascent hydrogen. 
We are, in fact, dependent upon this method for the prepara- 
tion of the alcohol. 

It is, like ordinary propyl alcohol, a colorless liquid. It 
boils at 85°. While all its reactions show that it is a hydroxide, 
under the influence of oxidizing agents it conducts itself quite 
differently from the alcohols thus far considered. It is con- 
verted first into acetone, C 3 H 6 0, which is isomeric with the 
aldehyde obtained from ordinary propyl alcohol ; by further 
oxidation, it however does not yield an acid of the formula 
CoH 6 2 , as we should expect it to, but breaks down, yielding 
two simpler acids; viz., formic acid, CH 2 2 , and acetic acid, 
C 2 H 4 2 . 

Secondary alcohols. — Secondary propyl alcohol is the 
simplest representative of a class of alcohols which are known 
as secondary alcohols. They are made by treating the ketones 
with nascent hydrogen, and are easily distinguished from other 
alcohols by their conduct towards oxidizing agents. Thev 
yield acetones containing the same number of carbon atoms, 
and then break down, yielding acids containing a smaller num- 
ber of carbon atoms. 

Is there anything in the structure of these secondary alcohols 
to suggest an explanation of their conduct? Secondary pro- 
pyl alcohol is made from acetone by treating with nascent 
hydrogen. Acetone contains two methyl groups and carbonyl. 



122 DERIVATIVES OF THE PARAFFINS. 

as represented by the formula CH 3 — CO— CH 3 . The sim- 
plest change that we can imagine as taking place in this com- 
pound under the influence of hydrogen is that represented in 
the following equation : — 

CH3-CO-CH3 + H 2 = CH3-CH.OH-CH3. 

The very close connection existing between acetone and second- 
ary propyl alcohol, and the fact that there are two methyl 
groups in acetone, make it appear probable that there are also 
two methyl groups in secondary propyl alcohol, as represented 
in the above equation. On the other hand, the easy transfor- 
mation of primary propyl alcohol into propionic acid, which can 
be shown to contain etlryl, shows that in the alcohol ethyl is 
present. Therefore, we may conclude that the difference 
between primary and secondary propyl alcohol is that the 
former is an ethyl derivative and the latter a di-methyl deriva- 
tive of methyl alcohol, as represented by the formulas : — 

r" 





OH ^ OH ^ OH 

Methyl alcohol. Ethyl methyl alcohol or Dimethyl methyl alco- 

ordinary propyl al- hoi or secondary 

cohol. propyl alcohol. 

Primary propyl alcohol is methyl alcohol in which one hydrogen 
is replaced by a radical, while secondary propyl alcohol is 
methyl alcohol in which two hydrogens are replaced by radicals. 
An examination of all secondary alcohols known shows that 
the above statement can be made in regard to all of them. 
They must be regarded as derived from methyl alcohol by the 
replacement of two hydrogen atoms by radicals. The alcohols 
of the first class, like methyl, ethyl, and ordinary propyl alco- 
hols, which are derived from methyl alcohol by the replacement 
of one hydrogen by a radical, are called primary alcohols. 
Another way of stating the difference between primary and 



BUTYL ALCOHOLS. 



123 



secondary alcohols is this : Primary alcohols contain the group 
CH 2 OH ; secondary alcohols contain the group CHOH. These 
statements necessarily follow from the first ones. 

A primary alcohol, when oxidized, yields an aldehyde and an 
acid containing the same number of carbon atoms as the 
alcohol does. 

A secondary alcohol, when oxidized, yields an acetone, and 
then an acid or acids containing a smaller number of carbon 
atoms. 

Recalling what was said regarding the nature of the changes 
involved in passing from an alcohol to the corresponding alde- 
hyde and acid, we see that the formation of the acid is impossi- 
ble in the case of a secondary alcohol. In the case of a 
primary alcohol, we have : — 

R r R 

H C J OH. 




O 10 

Alcohol. Aldehyde. Acid. 

(n the case of the secondary alcohol, we have : — 

R 
R 
H 



OH 

Secondary alcohol. Ketone. 

farther introduction of oxygen cannot take place without a 
breaking down of the compound. It will be seen that the 
formulas used to express the structure of the compounds are 
remarkably in accordance with the facts. 

Butyl alcohols, C 4 H 9 .OH. — Theoretically, there are two 
possible hydrox}d derivatives of each of the two butanes, 
making four butyl alcohols in all. They are all known. Two 
are primary alcohols. 



124 DERIVATIVES OF THE PARAFPIKS. 

1. Normal butyl alcohol, CH 3 .CH 2 .CH 2 .CH 2 .OH. 

2. Isobutyl alcohol, ^ 3 >CH.CH 2 OH. 

CH 3 

The third is a derivative of normal butane, and is a secondary 
alcohol. 

3. Secondary butyl alcohol, CH 3 .CH 2 .CH < ° H . This 

CH 3 

alcohol is prepared by treating ethyl-methyl ketone with nascent 
hydrogen : — 

CH 3 .CH 2 -CO-CH 3 + H 2 = CH 3 .CH 2 .CH< 0H . 

CH 3 

(Compare this with the reaction for making secondary propyl 
alcohol.) CH 3 

4. Tertiary butyl alcohol, CH 3 - C - OH. The fourth butyl 

CH 3 
alcohol has properties which distinguish it from the primary and 
secondary alcohols. When oxidized it yields neither an alde- 
hyde nor an acetone, but breaks down at once, yielding acids con- 
taining a smaller number of carbon atoms. Assuming that every 
primary alcohol contains the group CH 2 OH, and that every sec- 
ondary alcohol contains the group CHOH, it follows that the two 
primary butyl alcohols and secondary butyl alcohol must have 

the formulas above assigned to them ; and it follows further, that 

CH 3 
I 
the fourth butyl alcohol must have the formula CH 3 — C — OH, 

CH 3 

as this represents the only other arrangement of the constituents 
possible, according to our theory. This formula represents a 
condition which does not exist in either the primary or second- 
ary alcohols. It is methyl alcohol in which all the hydrogen 
atoms, except that in the hydroxyl, are replaced by methyl 
groups, and it contains the group C— (OH). Such an alcohol 
is known as a tertiary alcohol, and the one under consideration 



PENTYL ALCOHOLS. 125 

is called tertiary butyl alcohol. It is the simplest derivative of 
a class of which but few members are known. 

Tertiary butyl alcohol is made by a complicated reaction 
which cannot easily be interpreted; viz., by treating acetyl 
chloride, CEL.COCl, with zinc methyl, Zn(CH 3 ) 2 . These two 
substances unite, forming a crystallized compound ; and, when 
this is treated with water, it breaks up, yielding several products, 
among which is tertiary butyl alcohol. By taking other acid 
chlorides, and the zinc compounds of other radicals, other 
tertiary alcohols may be obtained. 

Characteristics of the three Classes of Alcohols. To recapitu- 
late briefly, we find, in studying the hydroxyl derivatives of the 
hydrocarbons, that they can be divided into three classes, ac- 
cording to their conduct towards oxidizing agents. 

To what was said above regarding the conduct of primary 
and secondary alcohols we can now add : Tertiary alcohols 
yield neither aldehydes nor acetones, but break down at once, 
yielding simpler acids. 

The general formulas representing these three kinds of alco- 
hols are : — 

H ° H aDd C R 



OH ^OH I OH 

Primary. Secondary. Tertiary. 



Note for Student. — Show how the formula for the tertiary alco- 
hols is in accordance with the fact that these alcohols clo not yield 
aldehydes nor ketones. 



Pentyl alcohols, C 5 H n .OH. — These alcohols are the hy- 
droxyl derivatives of the pentanes. Eight are possible, and 
seven of these are known. Only two of them need be con- 
sidered here. These are the so-called amyl alcohols. 



126 DERIVATIVES OF THE PARAFFINS. 

rjTT 

Inactive amyl alcohol, CH 3 > CH — CH 2 — CH 2 OH. — 

This alcohol, together with at least one other of the same 
composition, forms the chief part of the fusel oil obtained in 
the fermentation of sugar. By fractional distillation of fusel 
oil ordinary commercial amyl alcohol is obtained, as a colorless 
liquid, having a penetrating odor, and boiling at 131° to 132°. 
This can be separated by other methods into two isomeric 
alcohols, one of which is inactive amyl alcohol and the other 
active amyl alcohol. The names refer to the behavior of the 
substances towards polarized light, the former having no action 
upon it, the latter turning the plane of polarization 1 to the left. 
When oxidized, inactive amyl alcohol yields an acid contain- 
ing the same number of carbon atoms, and is, therefore, a 
primary alcohol. The acid has been made by simple reac- 
tions which show that it must be represented by the formula 

™3>CH.CH 2 .C0 2 H. Therefore, the alcohol has the structure 

represented by the formula ™ 3 > CH.CH 2 .CH 2 OH, 

CH 3 

pTT 

Active amyl alcohol, CH 3 .CH 2 .CH< CH 3 OH '— This, as 

has been stated, is obtained, together with the inactive alcohol, 
from fusel oil. Not enough is known about it to enable us to 
say with certainty whether the above formula represents its 
structure or not. It is a primary alcohol as represented. 

The remaining members of the series will not be considered, 
though a list of some of the more important ones is given 
below. As regards the naming of the alcohols, it is best to 
refer them to methyl alcohol, just as the hydrocarbons are 
referred to marsh gas. For this purpose methyl alcohol is 
called carbinol, and we then get such names as methyl-carbinol, 
di-ethyl-carbinol, etc., which convey at once an accurate idea 

1 This is not the proper place to explain exactly what is meant by these expressions. 
To the student of physics they convey definite meanings. To one who has not studied 
physics they are meaningless. 



NOMENCLATURE. 127 



concerning the structure of the substances. A few illustrations 
will suffice. Take the alcohols considered above : — 



Ethyl alcohol is methyl-carbinol, 



Primary propyl alcohol is ethyl-carbinol, C 




OH 



CH2CH2 
H 

H ' 
OH 

CH 3 



Secondary propyl alcohol is di-methyl- ) p J CH 3 
carbinol, j 1 H ' 



OH 
CH, 



OH 

Tertiary butyl alcohol is tri-methyl-carbinol, C -l 3 ; 

CHo 



OH 

CH 2 .CH< CH3 
CH, 



Inactive amyl alcohol is isobutyl-carbinol, C -l H 

H 



r 

l OH, etc., etc., 



a name given to it on account of the presence in it of the iso- 
butyl group CH 2 .CH < CR 3 . 

The following table will give an imperfect idea of the extent 
to which the series of alcohols derived from the paraffins is 
developed. There are thirteen hexyl alcohols and thirteen heptyl 
alcohols known. Of most of the higher members but one 
variety is known. They are not important, except in so far 
as they indicate the possibility of the discovery of other 
alcohols. 



128 



DERIVATIVES OF THE PARAFFINS. 



Methyl alcohol 


Ethyl 


u 


Propyl 


u 


Butyl 


a 


Pentyl 


a 


Hexyl 


a 


Heptyl 


a 


Octyl 


a 


Nonyl 


u 


Cetyl 


u 


Ceryl 


a 


Myricyl 


u 



ALCOHOLS OF THE METHYL ALCOHOL SERIES. 
Series C n H 2n + 1 .OH. 

CH 3 .OH. 
C 2 H 5 .OH. 
C 3 H 7 .OH. 
C 4 H 9 .OH. 
C 5 H n .OH. 
C 6 H 13 .OH. 
C 7 H 15 .OH. 
C 8 H 17 .OH. 
C 9 H 19 .OH. 
CieHgg.OH. 

C27H 55 .OH. 

C3oH 61 .OH. 

2. Aldehydes 

In general, it follows from what has been said concerning 
the properties of primary alcohols, that there should be an 
aldehyde corresponding to every primary alcohol. Many of these 
have been prepared. They resemble ordinary acetic aldehyde so 
closely that it is unnecessary to take them up individually. If 
we know the structure of the alcohol from which iai aldehyde is 
formed by oxidation, we also know the structure of the aldehyde. 

Besides the one method for the preparation of aldehydes 
which has been mentioned, viz., the oxidation of primary 
alcohols, there is one other which should be specially noticed. 
It consists in distilling a mixture of a formate and a salt of 
some other acid. Thus, if a mixture of an acetate and a 
formate be distilled, acetic aldehyde is formed as represented 
by the equation : — 

CH3.COOM CH C0H + MC0 
H.COOM 3 -r 2 3 

Aldehyde. 



FATTY ACIDS. 129 

This method has been used to a considerable extent in making 
the higher members of the series. 

Experiment 32. Mix about equal weights of dry calcium formate 
and dry calcium acetate. Distil from a small flask. Collect some of 
the distillate in water, and prove that aldehyde is formed. 

3. Acids. 

Formic and acetic acids are the first two members of an 
homologous series of similar acids, generally called the fatty 
acids, on account of the fact that several of them occur in large 
quantities in the natural fats. The names and formulas of 
some of the principal members are given iu the following 
table. The reasons for representing the acids as compounds 
containing the carboxyl group, C0 2 H, have been given, and 
need not here be restated : — 

FATTY ACIDS. 
Series C n H 2n + 1 .C0 2 H, or C^O,. 

Formic acid H.C0 2 H. 

Acetic " CH 3 .C0 2 H. 

Propionic » C 2 H 5 .C0 2 H. 

Butyric « C 3 H 7 .C0 2 H. 

Valeric " C 4 H 9 .C0 2 H. 

Caproic or 
Hexoic acids 
QEnanthvlic or 



1 C 5 H u .C0 2 H. 



C 6 H 13 .C0 2 H. 

Heptoic acids j 

°T? KC< ^ 1 C 7 H 15 .C0 2 H. 

Uctoic acids ) 

Pelargonicor | C 8 H 1? .C0 2 H. 

JNonoic acids ) 

Capric acid C 9 H 19 .C0 2 H. 



130 DERIVATIVES OF THE PARAFFltfg. 

Laurie acid CnH^.COsH. 

Myristic " C^H^.COgH. 

Palmitic " . C 15 H 31 .C0 2 H. 

Margaric " C^H^.COsH. 

Stearic " C^H^CC^H. 

Arachidic " C 19 H 39 .C0 2 H. 

Behenic " C 21 H 43 .C0 2 H. 

Hyenic " C 24 H 49 .C0 2 H. 

Cerotic " C 26 H 53 .C0 2 H. 

Melissic " C^H^.COsH. 



Although, as will be seen, a large number of fatty acids are 
known, most of them included in the list are at present merely 
curiosities, and need not be studied specially. Not more than 
six in addition to formic and acetic acids will require attention. 

Propionic acid, C 3 H 6 2 (C 2 H5.C0 2 H). — Propionic acid is 
formed in small quantity by the distillation of wood, and by the 
fermentation of various organic bodies, particularly calcium 
lactate and tartrate. It is prepared most readily by treating 
ethyl cyanide (propio-nitrile) with caustic potash : — 

C 2 H 5 .CN + KOH + H 2 = C 2 H 5 .C0 2 K -f NH 3 . 

Other methods for preparing it are the following : — 

(1) By reducing lactic acid with hydriodic acid. (This will 
be explained under the head of Lactic Acid, which see.) 

(2) By the action of carbon dioxide upon sodium ethyl : — 

C0 2 + NaC 2 H 5 = C 2 H 5 .C0 2 Na. 

It is a colorless liquid with a penetrating odor somewhat re- 
sembling that of acetic acid. It boils at 141°. (Compare with 
boiling-points of formic and acetic acids.) 



PROPIONIC ACID. 131 

It yields a large number of derivatives corresponding to 
those obtained from acetic acid. 

Note for Student. — What is propionyl chloride? and how can it 
be prepared? It is analogous to acetyl chloride. 

The simple substitution- products of propionic acid present an 
interesting and instructive case of isomerism. It is found that 
there are two chlor-propionic acids, two brom-propionic acids, 
etc. Those products which are obtained by direct treatment of 
propionic acid with substituting agents are called a-products, 
and the isomeric substances ^-products. Thus we have a-chlor- 
propionic and a-brom-propionic acid, made by treating propionic 
acid with chlorine and bromine ; and ^-chlor-propionic acid and 
ft-brom-propionic acid, made by indirect methods. The differ- 
ence between these two series of derivatives is due to different 
relations between the constituents. Our usual method of repre- 
sentation indicates the possibility of the existence of two iso- 
meric chlor-propionic acids, and of similar mono-substitution 
products of propionic acid. The acid is represented thus : — 

CH 3 .CH 2 .C(J 2 H. 

Now, if chlorine should enter into the compound, as represented 
by the formula CH 2 C1.CH 2 .C0 2 H, (1) we should have one of 
the chlor-propionic acids ; while, if it should enter as indicated 
in the formula CH 3 .CHC1.C0 2 H, (2) we should have the iso- 
meric product. We have thus two chlor-propionic acids actu- 
ally known, and our theory gives us two formulas. How can 
we tell which of the formulas represents a-chlor-propionic acid, 
and which the /2-acid? We can tell only by carefully study- 
ing all the reactions and methods of formation of both com- 
pounds. The best evidence is furnished by a study of the lactic 
acids, which will be shown to be mono-substitution products of 
propionic acid. It will be shown that a-chlor-propionic acid 
can be transformed into a lactic acid the structure of which is 
represented by the formula CH 3 .CH(OH).C0 2 H, and that, by 



132 DERIVATIVES OF THE PARAFFINS. 

replacing the hydroxy 1 of this lactic acid by chlorine, a-chlor- 
propionic acid is formed. It therefore follows that formula (2) 
above given is that of a-chlor-propionic acid, and formula (1) 
that of /?-chlor-propionic acid. Further, any mono-substitution 
product of propionic acid which can be made directly from 
a-chlor-propionic acid, or converted directly into this acid, is an 
a-product, and has the general formula 

CH 3 .CHX.C0 2 H; 

and, similarly, the /^-products have the general formula 

CH 2 X.CH 2 „C0 2 H, 
in which X represents any univalent atom or group. 

Butyric acids, C 4 H s 2 lC 3 H 7 .C0 2 H). 

Normal butyric add, CH 3 .CH 2 .CH 2 .C0 2 H. When butter is 
boiled with caustic potash, the potassium salts of butyric acid and 
of some of the higher members of the series are found in the solu- 
tion at the end of the operation. Butter, like other fats, belongs 
to the class of bodies known as ethereal salts ; and these, as we 
have seen, when boiled with the alkalies are decomposed, yielding 
alcohol and alkali salts of acids (saponification) . In the case of 
butter and of nearly all other fats, the alcohol formed is glycerin. 
Butyric acid occurs also in many other fats besides butter. 

It is made most readily b}^ fermentation of sugar by what is 
known as the butyric acid ferment. This ferment probably is 
contained in putrid cheese. Hence, to make the acid, sugar 
and tartaric acid are dissolved in water, and, after a time, 
certain quantities of putrid cheese and sour milk are added, 
and also some powdered chalk. At first the sugar is converted 
into glucose : — 

C^H^On -J- H 2 = 2 C 6 H 12 6 . 

Cane sugar. Glucose. 

The glucose breaks up, yielding lactic acid, C 3 H 6 8 : — 
C 6 H 12 6 = 2 C 3 H 6 (J 3 . 

Glucose. Lactic acid. 



VALERIC ACIDS. 133 

And, finally, the lactic acid is converted into butyric acid : — 
2 C 3 H 6 3 = C 4 H 8 2 + 2 C0 2 + 4 H. 

Other methods for the preparation of butyric acid are : — 

(1) By oxidation of normal butyl alcohol ; and 

(2) By treating normal propyl cyanide, CH 3 .CH 2 .CH 2 CN, 
with caustic potash. 

The acid is a liquid having an acid, rancid odor, like that of 
rancid butter. It boils at 163°. (Compare with the preceding- 
acids.) Like the lower members of the series it mixes with 
water in all proportions. 

Ethyl butyrate, C 3 H 7 .C0 2 C 2 H 5 , has a pleasant odor resembling 
that of pineapples. It is used under the name of essence oj 
pineapples. 

Isobutyric acid, SS 3 > CH.0O 2 H. — From the two propyl 

U±± 3 

alcohols the two chlorides, propyl chloride, CH 3 .CH 2 .CH 2 C1, 

prr 

and isopropyl chloride, 3 > CHC1, can be made, and from 
these the corresponding C} T anides, — 

Propyl cyanide CH 3 .CH 2 .CH 2 CN, 

CH 
and Isopropyl cyanide .... 3 > CHCN. 

CH 3 

By boiling with caustic potash, the former is converted into 
normal butyric acid, as stated above ; while the latter yields 

CH 
isobutyric acid, 3 > CH.C0 2 H. This acid can be prepared 

CH> 

CH 
also by oxidizing isobutyl alcohol, 3 >CH.CH 2 OH. It is 

CH 3 

found in nature in the carob bean. 

Isobutyric acid is a liquid which boils at 154°. Its odor is 
less unpleasant than that of the normal acid. 

Valeric acids, CsHioO.CCJIg.CCXrl). — Four carboxyl de- 
rivatives of the butanes are possible. Four acids of the 
formula C 5 H 10 O 2 are known. 



134 DERIVATIVES OF THE PARAFFINS. 

/-ITT 

Inactive or ordinary valeric acid, qtx 3 > CH.CH 2 .C0 2 H. 

— This acid is made by oxidizing inactive amyl alcohol. It 

can also be made (and this reaction reveals the structure of 

CH 

the acid) by starting with isobutvl alcohol, 3 > CH.CH 2 OH, 

converting this first into the chloride and then into the cyanide, 

CH 
and, finally, transforming the cyanide, which is 3 > CH.CH 2 CN, 

CH 3 

into the acid. It occurs in valerian root, whence its name. It 
is an unpleasant smelling liquid, boiling at 175°. It requires 
thirty parts of water for solution. 

Amyl valerate, C 4 H 9 . C0 2 C 5 H n , has the odor of apples, and is 
used under the name of essence of apples. 

Active valeric acid, ^S^x > CH.CH 2 .CH 3 . — This acid 
OL> 2 xi 

is prepared by oxidation of active amyl alcohol. Although the 

alcohol turns the plane of polarization to the left, the acid 
turns it to the right. The alcohol is said to be Icevo-rotatory, 
and the acid dextro-rotatory. 



The higher acids of the series are, for the most part, found 
in various fats. They are difficultly soluble in water. The 
highest members are solids. The two best known, because 
occurring in largest quantity, are palmitic and stearic acids. 
These are contained in combination with the alcohol, glycerin, in 
all the common fats. The fats will be treated under the head 
of Glycerin. 

Palmitic acid, C 15 H 31 .C0 2 H, can be made by saponifying 
many fats, but especially palm-oil, from which it is obtained 
mixed with only one other acid. 

It crystallizes in needles which melt at 62°. 

Stearic acid, Ci Y H 35 .C0 2 H, is the acid contained in that 
particular fat known as stearin. The so-called " stearin can- 



soaps. 135 

dies " are really made of a mixture of palmitic and stearic 
acids, and from them stearic acid can be separated in pure form 
by long-continued fractional crystallization from ether and 
alcohol. 

It crystallizes from alcohol in needles or lamina? which melt 
at 69°. 

Soaps. — In speaking of the decompositions of ethereal salts 
by boiling with alkalies, it was stated that this process is 
called saponification because it is best exemplified in the manu- 
facture of soaps from fats. The fats are themselves rather 
complicated ethereal salts. When they are boiled with an 
alkali, as caustic soda, the alcohol is liberated, and the alkali 
salts of the acids are formed. These salts are the soaps. They 
are in solution after the process of saponification is completed, 
and can be separated by adding a solution of common salt, in 
which they are insoluble. 

Experiment 33. In an iron pot boil about 25s of lard with a 
solution of caustic soda for two hours. After cooling, add a strong- 
solution of sodium chloride. The soap will separate and rise to the 
top of the solution, where it will finally solidify. Dissolve some of 
the soap thus obtained in water, and filter. Add hydrochloric acid, 
when the free fatty acids, mainly palmitic and stearic acids, will 
separate as solids, which will rise to the top. The hydrochloric acid 
simply decomposes the sodium palmitate and stearate, giving free 
palmitic and stearic acids and sodium chloride : — 



Sodium Palmitate. Palmitic Acid. 

and C n H 35 .C0 2 Na + HC1 = C n H 35 .C0 2 H + NaCl. 

Sodium Stearate. Stearic Acid. 



The remaining derivatives of the higher members of the 
paraffin series include the ethers, ketones, ethereal salts, 
mercaptans, sulphur ethers, sulphonic acids, cyanides and 
isocyanides, cyanates and isocyanates, sulpho-cyanates and 



136 DERIVATIVES OF THE PARAFFINS. 

iso-sulpho-cyanates, substituted ammonias and analogous com- 
pounds, metal derivatives, and nitro-derivatives. 

A great many substances belonging to these classes, and 
containing residues of the higher hydrocarbons, have been pre- 
pared and studied ; but, in the main, they so closely resemble 
the simpler substances which have alread}- been described that 
we should gain nothing by taking them up here individually. 
The student, however, is earnestly advised to apply the princi- 
ples discussed in the first part of the book to a few other cases. 
Thus, let him take propane and butane, and, not only write the 
formulas of the derivatives which can be obtained from them, 
but, above all, write the equations representing the action in- 
volved in their preparation, and the transformations of which 
they are capable. 

POLYACID ALCOHOLS AND POLYBASIC ACIDS. 

1. Di-acid Alcohols. 

The alcohols thus far considered are of the simplest kind. 
They correspond to the simplest metallic hydroxides, as potas- 
sium hydroxide, KOH. Just as these simplest metallic hydrox- 
ides are called mon-atid bases, so the simplest alcohols are 
called mon-acid alcohols, 1 expressions which are suggested b} r 
the term mono-basic acid. But, as is well known, there are 
metallic hydroxides, like calcium hydroxide, Ca(OH) 2 , barium 
hydroxide, Ba(OH) 2 , etc., which contain two hydroxyls, and 
are hence known as di-acid bases; and so, too, there are di-acid 
alcohols which bear to the mon-acid alcohols the same relation 
that the di-acid bases bear to the mon-acid bases. Only one 
alcohol of this kind, derived from the paraffin hydrocarbons, is 
well known. 

Ethylene alcohol or glycol, C 2 H 6 2 [C 2 H 4 (OH) 2 ]. —Glycol 
is made by starting with ethylene, a hydrocarbon of the formula 

1 The expression monatomic alcohols is used hy some writers, but, as it is confusing, 
it is gradually giving way to the more rational expression above used. 



ETHYLENE ALCOHOL. 137 

C 2 H 4 . When this is brought together with bromine, the two 
unite directly, forming ethylene bromide, C 2 H 4 Br 2 . By replacing 
the two bromine atoms by hydroxyl, ethylene alcohol or glycol 
is formed. 

It is a colorless, inodorous, somewhat oily liquid, which boils 
at 197.5°. It has a sweetish taste, and is hence called glycol 
(from jXvkvs, siveet) . Hence, further, the other alcohols of 
this series are also called glycols. 

The derivatives of ethylene alcohol are not as numerous as 
those of the better known members of the methyl alcohol series, 
but those which are known are of the same general character. 
The reactions of the alcohol are the same as those of the mon- 
acid alcohols, but it presents more possibilities. In most cases 
in which a mon-acid alcohol yields one derivative, ethylene 
alcohol yields two. Thus, with sodium, the two compounds, 

sodium glycol, C 9 H 4 < ^ a , and di-sodium glycol, C,H, < " a . 
OH ONa 

can be formed ; from these, by treating with ethyl iodide, the 

Of H 

two ethers, ethyl-glycol ether, C 2 H 4 < 2 5 , and di-ethyl-glycol 

OO H 

ether, C 2 H 4 < nr , 2 n 5 , are made. By treatment with hydro- 

CI 
chloric acid, the chloride, C 2 H 4 < , known as ethylene chlor- 

hydrine is formed ; and this, by treatment with phosphorus tri- 
chloride, can be converted into ethylene chloride, C 2 H 4 C1 2 , etc. 
Its conduct towards acids is like that of a di-acid base. It 
forms neutral and alcoholic salts, of which the acetates may 
serve as examples. Thus we have the 

Mono-acetate, C 9 H 4 < °- C 2 H 3° 
2 4 OH 

and the Di-acetate, C 9 H 4 < OC 2 H 3° . 

2 4 OC 2 H 3 0' 

the former still containing alcoholic hydroxyl and corresponding 
to a basic salt ; the latter being a neutral compound. 



138 DERIVATIVES OF THE PARAFFINS. 

The formation of the diacetate is a step in one of the methods 
of preparing ethylene alcohol. This method consists in treating 
ethylene bromide with potassium acetate in alcoholic solution, 
separating the acetates of ethylene thus formed, and decom- 
posing these by means of barium hydroxide. The reactions 
involved are represented by the following equations : — 

P tt ^Br KO.C 2 H 3 _ r w O.C 2 H 3 9 ^ n . 

C2H4< Br + KO.C 2 H 3 " ° 2H4< O.C 2 H 3 + 2 KBr ' 

and C 2 H 4 < ° - ° 2 g S ° +Ba < ^ = C 2 H 4 < °" +Ba(C 2 H 3 2 ) 2 . 

The alcohol can also be made by treating ethylene bromide 
with potassium carbonate : — 

C 2 H 4 < J* 1 ' + ^ >CO + H 2 == C 2 H 4 < ^ + 2 KBr + C0 2 ; 
Br KO OH 

and by treating ethylene bromide with silver oxide : — 

C 2 H 4 < * r + Ag 2 + H 2 = C 2 H 4 < ^ + 2 AgBr. 
Br OH 

These methods of formation show clearly what ethylene alcohol is. 
When acetyl chloride acts upon the alcohol at ordinary tem- 

Ap TT A 

perature, the product has the formula C 2 H 4 < 2 3 . This is 

also formed by the action of hydrochloric acid gas on the diace- 
tate. It seems probable, therefore, that the action of acetyl 
chloride is to be represented by two equations ; thus : — 

C ^< ?^ + 2 C 2 H 3 0C1 = C 2 H 4 < °C 2 H 3 + 2 HC1 . 
OH O0 2 H 3 U 

and C 2 H 4 < °°*?a° + HC1 = C 2 H 4 < ° C * H *° + C 2 H 4 2 . 
OC 2 H 3 OI 

There are two ways in which the structure of a compound 

of the formula C 9 H 4 (OH) 2 can be represented. They are, — 

CH 2 (OH) 
(1) I , in which each hydroxyl is represented in combi- 

CH 2 (OH) CH(OH) 2 

nation with a different carbon atom ; and (2) I , in which 

V y CH 3 

both hydroxyls are represented in combination with the same 



ETHYLENE ALCOHOL. 139 

carbon atom. The question at once suggests itself, to which of 
these formulas does ethylene alcohol correspond? To answer 
this question, we must recall what was said regarding the two 
dichlor-ethanes, known as ethylene chloride and ethylidene chloride. 
The former of these corresponds to the formula CH 2 C1.CH 2 C1, 
while the latter, which is formed from aldehyde hy replacing the 
carbonyl oxygen by two chlorine atoms, is represented by the 
formula CHC1 2 .CH 3 . When the chlorine atoms of ethylene 
chloride are replaced by hydroxyl, ethylene alcohol is produced. 

CH 2 (OH) 
Hence, the alcohol has the formula I , or each of the 

CH 2 (OH) 

hydroxyls is in combination with a different carbon atom. 

All attempts to make the isomeric di-acid alcohol correspond- 
ing to ethylidene chloride, and having both hydroxyls in combi- 
nation with the same carbon atom, as represented in the formula 

CH(OH 2 ) 

I , have failed. Instead of getting ethylidene alcohol, 

CH 3 

aldehyde is generally obtained. Aldehyde is ethylidene alcohol 

minus water : — 

CH(OH) 2 CHO 

I = I 4- H 2 0. 

CH 3 CH 3 

It is believed that one carbon atom cannot, under ordinary 
circumstances, hold in combination more than one Irydroxyl 
group. If this is true, then ethylidene alcohol cannot be pre- 

ATT 

pared any more than the hypothetical carbonic acid, CO < , 

can be. So, too, the simplest di-acid alcohol conceivable, 
viz., metlrylene alcohol, CH 2 (OH) 2 , cannot exist, but would 
break up, if formed at all, into water and formic aldehyde : — 

CH 2 (OH) 2 = H 2 + H.CHO. 

(See discussion regarding the transformation of alcohol into 
aldehyde, pp. 64-66.) 



140 DERIVATIVES OF THE PARAFFINS. 

Ethyl alcohol, as was pointed out, may be regarded either as 
ethane in which one hydrogen is replaced by hydroxyl, or as 
water in which one hydrogen is replaced by the radical C 2 H 5 , or 
ethyl. Ethyl, like all the radicals contained in the mon-acid 
alcohols, is univalent. It is ethane less one atom of hydrogen, 
just as methyl is methane less one atom of hydrogen. Each 
has the power of uniting with one atom of hydrogeD, or another 
univalent element, or of taking the place of one atom of 
hydrogen. 

If we take away two atoms of hydrogen from methane and 
ethane, we have left the residues or radicals CH 2 and C 2 H 4 . 
These can unite with two atoms of hydrogen, or take the place 
of two atoms of hydrogen, and they are hence called bivalent 
radicals. 

Just as ethylene alcohol may be regarded as ethane in which 
two hydrogen atoms are replaced by hydroxyls, so it ma}' be 
regarded as water in which the bivalent radical ethylene re- 
places two hydrogens belonging to two different molecules of 
water : — 

°^H 0< H 

Two molecules water. Ethylene alcohol. 



The higher members of the series of di-acid alcohols will not 
be considered here. 

2. Dibasic Acids. 

Just as there are di-acid alcohols derived from the paraffins, 
so there are dibasic acids which may also be regarded as deriva- 
tives of the paraffins. We have seen that the simplest acids, 
the monobasic fatty acids, are closely related to formic and 
carbonic acids ; that they may be regarded as derived from the 
latter by replacement of a hydroxyl by a radical, or as derived 



DIBASIC ACIDS. 141 

from the paraffins by the introduction of the group carboxyl, 
C0 2 H. The conditions existing in this group are essential to 
the acid properties. If two carboxyls are introduced into marsh 
gas, a substance of the formula CH 2 (C0 2 H) 2 is formed, and 
this is a dibasic acid. It contains two acid hydrogens, and 
is capable of forming two series of salts, the acid and neutral 
salts, like other dibasic acids. It ma}' be regarded also as 
derived from two molecules of carbonic acid by the replacement 
of two hydroxyls by the bivalent radical CH 2 : — 



OH CO< 



CH 2 



CO<9? CO< OH 

UH 
Two molecules carbonic acid. Dibasic acid. 

The general methods of preparation available for the building 
up of the series of dibasic acids are modifications of those used 
in making the monobasic acids. They are : — 

1. Oxidation of di-acid primary alcohols. Just as a mon- 
acid primary alcohol, R.CH 2 OH, yields by oxidation a mono- 
basic acid, so a cli-acid primary alcohol, R"(CH 2 OH) 2 , yields a 
dibasic acid, R"(C0 2 H) 2 . 

2. Treatment of the dicyanides, E"(CN) 2 , with caustic alkalies. 

3. Oxidation of the so-called hydroxy-acids or alcohol acids. 

These are compounds which are at the same time alcohol and 

acid ; as, for example, hydroxy- acetic acid, which is acetic acid 

in which one of the hydrogen atoms of the hydrocarbon residue, 

methyl, has been replaced by Irydroxyl, as represented in the 

CH 2 OH 
formula I . When this is oxidized, the alcoholic portion, 

C0 2 H 

CH 2 OH, is converted into carboxyl, and a dibasic acid is formed. 

4. From the cyanogen derivatives of the monobasic acids, 

CN 
such as cyan-acetic acid, CH 2 < , by the transformation of 

C0 2 H 

the cyanogen group into carboxyl. 



142 DERIVATIVES OF THE PARAFFINS. 

DIBASIC ACIDS, C n H 2n 2 4 . 

Oxalic acid . (C0 2 H) 2 . 

Malonic "....... CH 2 (C0 2 H) 2 . 

Succinic " C 2 H 4 (C0 2 H) 2 . 

Pyrotartaric " . C 3 H 6 (C0 2 H) 2 . 

Adipic "....... C 4 H 8 (C0 2 H) 2 . 

Pimelic " C 5 H 10 (CO 2 H) 2 . 

Suberic " C 6 H 12 (C0 2 H) 2 . 

Azelaic " C 7 H 14 (C0 2 H) 2 . 

Sebacic " C 8 H 16 (C0 2 H) 2 . 

Brassylic " C 9 H 18 (C0 2 H) 2 . 

Roccellic " C 15 H 30 (CO 2 H) 2 . 



Of the many acids included in this list onty four or five can 
be said to be well known. We may confine our attention to the 
first four members. 

Oxalic acid, C 2 H 2 4 [(C0 2 H) 2 ]. — In one sense, according to 
the accepted definition, oxalic acid is not a member of the series 
with which we are dealing, as it is not derived from a hydro- 
carbon by replacement of hydrogen by carboxyl ; nor is it 
derived from two molecules of carbonic acid by replacement of 
two hydroxyls by a bivalent radical. Still it is in other respects 
so closely allied to the members of the series, and has so many 
things in common with the other members, that it would be a 
mere act of pedant^ to consider it in any other connection. 

Oxalic acid occurs ve^ widely distributed in Nature ; as in 
certain plants of the oxalis varieties, in the form of the acid 
potassium salt ; as calcium salt in many plants ; in urinary 
calculi ; and as the ammonium salt in guano. 

It is formed by the action of nitric acid upon many organic 



OXALIC ACID. 143 

substances, particularly the different varieties of sugar and the 
so-called carbohydrates, such as starch, cellulose, etc. 

Experiment 34. In a good-sized flask pour half a litre of ordinary 
concentrated nitric acid (of specific gravity 1.245) upon 50s of sugar. 
Heat gently until the reaction begins. Then withdraw the flame, when 
the oxidation will proceed with some violence, and accompanied by 
a copious evolution of red fumes. When the action has ceased, 
evaporate the liquid to one-sixth the original volume, and let it 
cool, when oxalic acid will crystallize out. Recrystallize from water 
the acid thus obtained, and with the pure substance perform such ex- 
periments as will exhibit its properties. For example, (1) Heat a 
specimen at 100°, and notice loss of water; (2) Heat some in a small 
flask with sulphuric acid, and prove that both oxides of carbon are 
formed. 

On the large scale, oxalic acid is made by heating wood 
shavings or saw-dust with caustic potash and caustic soda to 
240° to 250°. The mass is extracted with water, and the solu- 
tion evaporated to crystallization, when sodium oxalate is de- 
posited. 

Other methods, which are interesting from a purely scientific 
point of view, are the following : — 

1 . The spontaneous transformation of an aqueous solution of 
cyanogen : — 

CN CO,H 

| + 4H 2 = 1 + 2NH 3 ; 

CN C0 2 H 

CN C0 2 (NH 4 ) 

or, really, | -f 4 H 2 = | 

CN C0 2 (NH 4 )' 

2. Treatment of carbon dioxide with sodium : — 

2 C0 2 + 2 Na = C 2 4 Na 2 . 

3. Heating sodium formate : — 

2H.C0 2 Na = C 2 4 Na 2 -4- 2 H. 
Oxalic acid crystallizes from water in monoclinic prisms con* 



144 DERIVATIVES OP THE PARAFFINS. 

taining two molecules of water (C 2 H 2 4 -f- 2 H 2 0) . It loses 
this water at 100°. It sublimes without decompositiou at 150° 
to 160°, but, if heated higher, it breaks up into carbon monox- 
ide, carbon dioxide, and formic acid : — 

2 C 2 H 2 4 = 2 C0 2 + CO + HC0 2 H + H 2 0. 

Sulphuric acid decomposes it into carbon monoxide, carbon 
dioxide, and water. Heated with glycerin to 100°, carbon 
dioxide and formic acid are formed (see Formic Acid) : — 

C 2 H 2 4 = C0 2 + H.C0 2 H. 

It is an excellent reducing agent, and is used as a standardize! 
in preparing solutions of potassium permanganate. 

Experiment 35. Try the action of a solution of potassium per- 
manganate on a solution of oxalic acid. Why is it best to have the 
solution of the permanganate acid? 

Oxalic acid is an active poison. It is used in calico printing. 

/Salts of oxalic acid. Like all dibasic acids, oxalic acid forms 
acid and neutral salts with metals. All the salts are insoluble 
except those containing the alkalies. Among those most com- 
mon are the acid potassium salt, C 2 4 HK, which is found in the 
sorrels or plants of the oxalis variety ; the ammonium salt, 
C 2 4 (NH 4 ) 2 , of which some urinary calculi are formed; and 
calcium oxalate, C 2 4 Ca, which, being insoluble in water and 
acetic acid, is used as a means of detecting calcium in the 
presence of magnesium. 

Malonic acid, C 3 H 4 4 [> CH 2 (C0 2 H) 2 ]- — This acid was first 
made by oxidation of malic acid (which see), and is hence 
called malonic acid. It can best be made by starting with 
acetic acid. The necessary steps are: (1) making chlor-acetic 
acid ; (2) transforming chlor-acetic acid into cyan-acetic acid ; 
(3) heating cyan-acetic acid with an alkali. 

Note for Student. — Write the equations representing the three 
steps mentioned. 



SUCCINIC ACIDS. 145 

It is a solid which crystallizes in laminae. It breaks up at a 
temperature above 132°, which is its melting-point, into carbon 
dioxide and acetic acid : — 

CH 2<™2 = CH 3 .C0 2 H + C0 2 . 
CU 2 xi 

Note for Student. — What simple method for the preparation of 
marsh gas and other paraffins is this reaction analogous to? 

Succinic acids, C,Hfi0 4 |> C 2 H 4 (C0 2 H) 2 ]. — Considering 
these acids as derived from ethane by replacing two hydrogens 
with carboxyl, we see that there may be two corresponding to 
ethylene and ethylidene chlorides. Two are actually known. 
One is the well-known succinic acid ; the other is called iso- 
succinic acid, 

0H 2 .CO 2 H 

Succinic acid, Ethylene succinic acid, I . — 

CH 2 .0O 2 H 

This acid occurs in amber (hence its name, from Lat. succinum, 
amber) ; in some varieties of lignite ; in many plants ; and in 
the animal organism, as in the urine of the horse, goat, and 
rabbit. 

It is formed under many circumstances, especially by oxida- 
tion of fats with nitric acid, by fermentation of calcium malate, 
and, in small quantity, in the alcoholic fermentation of sugar. 
Among the methods for its preparation are : — 

CH 2 .CN 

1. Treatment of ethylene cyanide, | , with a caustic 
alkali:— CH 2 .CN 

CH 2 CN CH 2 .C0 9 K 

| + 2 KOH + 2 H 2 =| +2 NH 3 . 

CH 2 CN CH 2 .C0 2 K 

2. Similarly, by treatment of /?-cyan-propionic acid with an 
alkali. (What is /?-cyan-propionic acid?) 

3. Reduction of tartaric and malic acids by means of 



146 DERIVATIVES OF THE PARAFFINS. 

hydriodic acid. These well-known acids will be shown to be 
closely related to succinic acid, and the reaction here mentioned 
will be explained. The methods actually used in the prepara- 
tion of succinic acid are: (1) the distillation of amber, and 
(2) the fermentation of calcium malate. 

The acid crystallizes in monoclinic prisms, which melt at 
180° (try it). It boils at 235°, at the same time giving off 
water, and being converted into the anhydride : — 

Among the salts ferric succinate, CJ^C^ . Fe (OH) , is of 
special interest, as it is entirely insoluble in water, and can 
therefore be used for the purpose of separating iron from 
manganese quantitatively. 

Experiment 36. Make a neutral solution of ammonium succinate 
by neutralizing an aqueous solution of the acid, and boiling off all 
excess of ammonia. Add some of this solution to a solution known to 
contain manganese and iron in the ferric state. A brown-reel precipi- 
tate will be formed. Filter and wash, and examine the filtrate for iron. 

CH(C0 2 H) 2 
Isosuccinio acid, Ethylidene succinic acid, I 

CH 3 
This acid is made by treating a-cyan-propionic acid with an 

alkali. (What is a-cyan-propionic acid ?) 

Isosuccinic acid forms crystals which melt at 130°. Heated 

to 150° it breaks up into propionic acid and carbon dioxide : — 

CH(C0 2 H) 2 CH 2 .C0 2 H 
I =1 + C0 2 . 

CH 3 CH 3 

Isosuccinic acid. Propionic acid. 

Note for Student. — Notice carefully the difference between the 
two succinic acids, as shown by their conduct when neatecl. What is 
the difference? 

Acids of the formula C,H 8 4 [= C 3 H 6 (C0 2 H) 2 ]- — Four 
acids of the formula C 5 H 8 4 are known, only one of which, 
however, need be considered here. This is, — 



• GLYCERIN. 147 

t^, + * ■ Q ^H CH ^7 H - C ° 2H ._ As the name indi- 
Pyrotartanc acid, ^ CQ ^ A 

cates, this acid is made by heating tartaric acid. The reactions 
which take place are complicated, and cannot well be represented 
by equations. The reactions which point to the above formula 
are also comparatively complicated, and their discussion at this 
time would tend only to confuse the student. 

Tri-acid Alcohols. 
The existence of m on-acid alcohols corresponding to the 
mon-acid bases, like potassium hydroxide, and of di-acid alco- 
hols corresponding to the di-acid bases, like calcium hydroxide, 
suggests the possible existence of tri-acid alcohols correspond- 
ing to tri-acid bases, like ferric hydroxide. There is only one 
alcohol of this kind derived from the paraffin hydrocarbons that 
is at all well known. This is the common substance glycerin. 

Glycerin, s H s O 3 . — As has been stated repeatedly, glycerin 
occurs very widely distributed as the alcoholic or basic constit- 
uent of the fats. The acids with which it is in combination are 
mostly members of the fatty acid series, though one, viz., oleic 
acid, which is found frequently, is a member of another series. 
Besides oleic acid, the two acids most frequently met with in 
fats are palmitic and stearic acids. When a fat is saponified 
with caustic potash, it yields free glycerin and the potassium 
salts of the acids. The reactions in the case of the glycerin 
compounds of palmitic and stearic acids are these : — 

Formation. 
rOH HO.OC.C 15 H 31 rO.CO.C 15 H 31 

C 3 hJ OH + HO.OC.C 15 H 31 = C 3 hJ O.CO.C 15 H 31 + 3HA 
I OH HO.OC.C^ C0.C0.C 15 H 31 

„ , . . . , Glycerin tri-palmitate, 

Glycerin. Palmitic acid. or p a lmitin. 



148 DEEIVATIVES OF THE PARAFFINS. 



rOH HO.OC.CyG^ 
C 3 H 5 ] OH + HO.OC.CtfH*,, = 
(oh HO.OC.C 17 H35 

Glycerin. Stearic Acid. 


r O.OC.d^ 
C 3 hJ O.OC.C 17 H85 + 3H 2 0. 
(.O.OC.C^H^ 

Glycerin tri-stearate, or 
Stearin. 




Saponification. 






C 3 H 5 - 


^O.OC.C 15 H 31 

O.OC.C 15 H 31 + 3KOH = 
,O.OC.C 15 H 31 

Palmitin. 


: C3H 5 (OH) 3 + 3C 15 H 31 

Glycerin. Potassium 


.C0 2 K. 

palmitate. 



O.OC.C^Hgs 
■J ■{ O.OC.C 17 H« + 3K0H = C 3 H 5 (OH) 3 + 3 C 17 H 35 . C0 2 K. 

O.OC.CnHq* Glycerin. Potassium stearate. 

Stearin. 

The fats are also decomposed by superheated steam, yielding 
free glycerin and the free acids, and this method is used on the 
large scale, a little lime being added to facilitate the process. 
Lead oxide decomposes fats yielding a mixture of glycerin and 
the lead salts of the acids. The mixture is known in medicine 
as " lead plaster." 

Glycerin is formed in small quantity by the alcoholic fermen- 
tation of sugar. 

It has been made synthetically from propylene chloride, 
C 3 H 6 C1 2 . The necessary steps are : (1) treatment with chlorine, 
giving C 3 H 5 C1 3 ; (2) treatment of the tri-chlorine derivative 
with water, thus replacing the three chlorine atoms by hydroxyl. 

Glycerin is a thick colorless liquid, with a sweetish taste 
(compare with glycol) . It mixes with alcohol and water in all 
proportions. It attracts moisture from the air. At low tem- 
peratures it solidifies, forming deliquescent crystals which melt 
at 17°. Under diminished pressure it can be distilled ; but, if 
heated to its boiling-point under the ordinary atmospheric pres- 
sure it undergoes decomposition. It is volatile with water 
vapor. 



GLYCERIN. 149 

Experiment 37. Heat a little glycerin in a dry vessel, and try to 
boil it. What evidence have yon that it undergoes decomposition? 
Put 20 cc to 30 cc glycerin in 400 cc to 500 cc water in a flask ; connect with 
a condenser, and boil. Prove that glycerin passes over with the water 
vapor. 

The reactions of glycerin all clearly lead to the conclusion 
that it is a tri-acid alcohol. 

(1) The three hydroxyl groups can be replaced successively 
by chlorine, giving the compounds, — 

{CI 
(OH)o' 

{CI 
OTT ' 

and Trichlorhydrin, C 3 H 5 C1 3 , 

which last compound is propane in which three hydrogen atoms 

are replaced by chlorine, or trichlorpropane. 

(2) It forms three classes of ethereal salts containing one, 
two, and three acid residues respectively. For example, with 
acetic anhydride these reactions take place : — 

r OH ( O.C 2 H 3 

1. C 3 hJ OH + (C 2 H 3 0) 2 =C 3 hJ0H + C 2 H 4 2 - 

(.OH (OH 

r OH / OC 2 H 3 

2. C 8 hJ OH + 2 (C 2 H 3 0) 2 = C 3 hJ OC 2 H 3 + 2 C 2 H 4 2 - 

(OH (OH 

/ OH ( OC 2 H 3 

3. C 3 H 5 ) OH + 3 (C 2 H 3 0) 2 = C 3 H 5 < OC 2 H 3 + 3 C 2 H 4 2 - 

( OH ( OC 2 H 3 

In regard to the relations of the hydroxyl groups to the parts 
of the radical C 3 H 5 , we have very little experimental evidence, 
though it appears highly probable that each hydroxyl is in 
combination with a different carbon atom as represented in the 
CH 2 OH 
I 
formula CHOH . 



150 DERIVATIVES OF THE PARAFFINS. 

In the first place, we have seen above that compounds con- 
taining two hyclroxyls in combination with the same carbon 
are not readily formed, if they are formed at all, and we have 
had some reason for concluding that this kind of combination 
is impossible. It would follow from this that the simplest tri- 
acid alcohol must contain at least three atoms of carbon, just 
as the simplest di-acid alcohol must contain at least two atoms 
of carbon. We have seen that the simplest tri-acid alcohol 
known does coutain three atoms of carbon. 

CH 2 OH 
I 

further, if the formula of glycerin is CHOH , it contains two 

CH 2 OH 
primary alcohol groups, CH 2 OH, and we have seen that this 
group is converted into carboxyl under the influence of oxidiz- 
ing agents. Therefore, we should expect by oxidizing glycerin 

COJEL C0 2 H 

I I 

to get products of the formulas, CHOH , and CHOH. Such prod- 

CH 2 OH C0 2 H 

ucts actually are obtained, the first being glyceric acid (which 
see) , and the second tartronic acid (which see) . 

Just as ethyl alcohol is regarded as water in which one 

C H ) 

hydrogen is replaced by the univalent radical C 2 H 5 , as 2 5 > O \ 

and glycol is regarded as water in which two hydrogen atoms 
of two molecules of water are replaced by the bivalent radical 

H >0 
C9H4, as C 2 H 4 ; so also glycerin may be regarded as water 
H >0 

in which three hydrogen atoms of three molecules are replaced 
by the trivalent radical C 3 H 5 , thus : — 



H.OH 


(OH 


H.OH 


C3HJOH 


H.OH 


(oh 


Three molecules water. 


Glycerin. 



BUTTER. 151 

Ethereal salts of glycerin. — Among the important 
ethereal salts of glycerin arc the nitrates. Two of these are 

rO.N0 2 
known ; viz., the mono-nitrate, C 3 H 5 -J OH , and the tri-nitrate, 

I OH 
C 3 H 5 (ON0 2 ) 3 , the latter being the chief constituent of nitro- 
glycerin. Nitro-glycerin is prepared by treating glycerin with 
a mixture of concentrated sulphuric and nitric acids. It is a 
pale yellow oil which is insoluble in water. At —20° it 
crystallizes in long needles. It explodes very violently by 
concussion. It can be burned in an open vessel, but if heated 
above 250° it explodes. Dynamite is infusorial earth impreg- 
nated with nitro-glycerin. Nitro-glycerin is the active constitu- 
ent of a number of explosives. 

Fats. — The relation of the fats to glycerin has already been 
stated. Here it will be necessary only to mention the composi- 
tion and characteristics of some of the more common fats. 

Most fats are mixtures of the three neutral ethereal salts 
which glycerin forms with palmitic, stearic, and oleic acids, 
and which are known by the names palmitin, stearin, and ole'in. 
Ole'in is liquid, and the other two fats are solids, stearin having 
the higher melting-point. Therefore, the larger the proportion 
of olei'n contained in a fat the softer it is, while the greater the 
proportion of stearin the higher its melting-point. Among the 
fats which are particularly rich in stearin may be mentioned 
mutton tallow, beef tallow, and lard. Human fat and palm oil 
are particularly rich in palmitin. Sperm oil and cod-liver oil 
are rich in olei'n. 

Butter consists of ethereal salts of glycerin and the follow- 
ing acids : myristic, palmitic, and stearic acids, which are not 
volatile, and butyric, caproi'c, caprylic, and capric acids, which 
are volatile with water vapors. All the acids mentioned are 
members of the fatty acid series. Some of these acids are 
soluble and some are insoluble in water. The percentage of 



152 DERIVATIVES OF THE PARAFFINS. 

insoluble fatty acids contained in butter has been found to be 
88 per cent. As the proportion of insoluble fatty acids con- 
tained in artificial butters, such as the so-called oleo-margarin, 
is greater than that contained in butter, it is not a difficult 
matter to distinguish between the two by determining the 
amount of these acids contained in them. 



Tri-basic Acids. 

Tri-carballylic acid, C 3 H5(C0 2 H)3. — This acid can be 
made from trichlorhydrin, C 3 H 5 C1 3 (which see), by replacing 
the chlorine by cyanogen, and heating with an alkali the tri- 
cyanhydrine thus obtained. It can be made also by treating 
aconitic acid (which see) with nascent Irvdrogen. It crystallizes 
from water in rhombic prisms which melt at 157° to 158°. 

Tetr-acid Alcohols. 

Erythrite, C 4 Hio0 4 [= C 4 H 6 (OH) 4 ]. — This substance occurs 
in one of the algae (Protococcus vulgaris) and in several lichens. 
It crystallizes from water in quadratic prisms. It has a very 
sweet taste. The fact that the simplest tetr-acid alcohol con- 
tains four atoms of carbon should be specially noted. 



There is no well known tetra-basic acid derived from the 
hydrocarbons of the paraffin series. 



Pent -acid Alcohols. 



By the reduction of the two sugars, xylose and arabinose, 
two pent-acid alcohols, xylite and arabite, have been made. 
Both have the formula C 5 H 12 5 [= C 5 H 7 (OH) 5 ]. 



HEX-ACID ALCOHOLS. 153 

No penta-basic acid belonging to this series is known. 



Hex- acid Alcohols. 

There are several hex-acid alcohols known. Most of them are 
derived from hexane, and have the composition represented by 
the formula C 6 H 8 (OH) 6 . It will be noticed that these hex-acid 
alcohols contain six carbon atoms each. 

Mannite, C 6 H 8 (OH) 6 . — Mannite is widely distributed in 
the vegetable kingdom. It occurs most abundantly in manna, 1 
which is the partly dried sap of the manna-ash (Fraxi7ius 
ornus) . It is obtained from incisions in the bark of the tree. 

Mannite is formed in the lactic acid fermentation of sugar. 
It is formed also by the action of nascent hydrogen on fructose 
and mannose. This indicates a close relationship between the 
sugars and mannite. Mannite crystallizes in needles, or 
rhombic prisms, which are easily soluble in water and in 
alcohol. It has a sweet taste. 

Nitric acid converts mannite into saccharic acid (which see) . 
When boiled with concentrated hydriodic acid, it is converted 
into secondary hexyl iodide, C 6 H 13 I. 

Mannite hexa-nitrate (nitro-mannite), C 6 H 8 (O.N0 2 ) 6 , is 
formed by treating mannite with a mixture of concentrated 
sulphuric and nitric acids. It is a solid substance and is very 
explosive. (Analogy with nitro-glycerin.) 

Mannite hex-acetate, 6 H. 8 (O.C 2 H 3 0) 6 , is formed by treat- 
ing mannite with acetic anhydride. Its formation, as well as 
that of the hexa-nitrate, shows that mannite is a hex-acid alcohol. 
For the purpose of making the acetates, acetic anhydride is 
sometimes used instead of acetyl chloride. In some cases in 

1 The manna of the Scriptures was obtained from the branches of Tammarix gallica. 
It contained no mannite, but a substance of similar properties. 



154 DERIVATIVES OF THE PARAFFINS. 

which the latter will not work, the former answers very well. 
Hence acetic anhydride has come into use as a reagent, which 
enables us to decide whether a substance under examination is 
or is not an alcohol ; and, if it is, to which class (whether 
mon-acid, di-acid, tri-acid, etc.) it belongs. 

There are three varieties of mannite — the ordinary, known as 
dextro-mannite, and, further, levo-mannite, and inactive mannite. 

Dulcite, C 6 H 8 (OH)6. — This occurs in a kind of manna 
obtained fmm Madagascar, the source of which, however, is 
unknown. It is formed by treating sugar of milk or galactose 
with nascent hydrogen (compare with mannite in this respect) . 

Nitric acid oxidizes dulcite, forming mucic acid (which see), 
isomeric with saccharic acid, which is formed from mannite. 
Like mannite, when boiled with hydriodic acid it yields second- 
ary hexyl iodide, C 6 H 13 I. 

Sorbite, CeHsCOH^. — Ordinary sorbite occurs in the berries 
of the mountain ash, and in many other fruits, as plums, cher- 
ries, apples, etc. It is formed by reduction of glucose. This 
variety is known as dextro-sorbite, because it is formed from 
glucose, which is dextro-rotatory. Levo-sorbite is also known, 
having been obtained by the reduction of one of the sugars. 



There are no hexa-basic acids known belonging to this series. 



Hept-acid Alcohols, etc. 

Perseite, C 7 H 9 (OH) 7 , occurs in the fruit and leaves of 
Laurus persea, and has been made artificially from dextro- 
mannose. Mannose is an aldehyde, and therefore has the power 
to take up hydrocyanic acid. The compound thus formed can 
be transformed into an acid, and it is by reduction of this acid 
that perseite is made. It is also called dextro-mannoheptite. 
B} r a similar reaction an oct-acid and a non-acid alcohol have 
been made. 



CHAPTER X. 

MIXED COMPOUNDS. -DERIVATIVES OF 
THE PARAFFINS. 

Under this head are included such compounds as belong 
at the same time to two or more of the chief classes already 
studied. Thus, there are substances which are at the same 
time alcohols and acids. There are others which are at the 
same time alcohols and aldehydes, alcohols and ketones, acids 
and ketones, etc. Fortunately, for our purpose, the number 
of compounds of this kind actually known is comparatively 
small, though among them are many of the most important 
natural compounds of carbon. The first class which presents 
itself is that of the alcohol acids or acid alcohols ; that is, sub- 
stances which combine within themselves the properties of both 
alcohol and acid. The} T are commonly called oxy -acids or 
hydroxy -acids. 

Hydroxy- acids, CnHonOg. 

These acids may be regarded either as monobasic acids into 
which one alcoholic hydroxyl has been introduced, or as mon- 
acid alcohols into which one carboxyl has been introduced. As 
their acid properties are more prominent than the alcoholic 
properties, they are commonly referred to the acids. Running 
parallel, then, to the series of fatty acids, we may look for a 
series of hydroxy-acids, each of which differs from the corres- 
ponding fatty acid by one atom of oxygen, or by containing one 
hydroxyl in the place of one hydrogen, thus : — 



156 DERIVATIVES OF THE PARAFFINS. 





Fatty acids. 


Hydroxy-acids. 


Formic acid . . 


H .C0 2 H 


HO.C0 2 H. 


Acetic acid . . 


. CH 3 .C0 2 H 


CH,< 0H 
2 C0 2 H 


Propionic acid . 


C2H5.CO9H 


C 2 H 4 < OH 
2 4 C0 2 H 

etc. 




etc. 



The first member of the series, which by analogy would be 
called hydroxy -formic acid, is nothing but the ordinary hypo- 
thetical carbonic acid. Although its relation to formic acid is 
the same as that of the next member of the series to acetic 
acid, it certainly has no properties in common with the alcohols ; 
but, owing to its peculiar structure, it is a dibasic acid which 
the other members of the series are not. Nevertheless, it may 
be referred to here for the sake of a few of its derivatives, 
which are somewhat allied to those of the hydroxy-acids proper. 

Carbonic acid, H 2 C0 3 ( CO < Q^Y — It is believed that 

this body exists in solutions of carbon dioxide in water. All 
that is known about it is that it is a feeble dibasic acid, and 
breaks up into water and carbon dioxide whenever it is set free 
from its salts. We have seen that this instability is generally 
met with in compounds containing two hydroxyls in combina- 
tion with one carbon atom. 

Among the derivatives of carbonic acid which may be re- 
ferred to at this time are the ethereal salts. These may be 
made : — 

1. By treating silver carbonate, CO< ®, with the iodides 
of alcohol radicals ; as, for example, — 

C0 <^f g + 2 C A X = co <™^ 5 + 2 A S L 
OAg OC 2 H 5 

2. By treating the alcohols with carbonyl chloride, COCl 2 :— • 

COCl 2 + 2 C 2 H 5 OH = CO(OC 2 H 5 ) 2 + 2 HC1. 



ETHYL CHLOR-CARBONATE. 157 



CI 
Ethyl chlor-carbonate, CO < ^ ~ „ . — This compound 

UL/ 2 ±1 5 

is made by treating alcohol with carbonyl chloride : — 

COCl 2 + C 2 H 5 OH = CO < ^ tt + HC1. 

(JG 2 ±i 5 

It may be regarded as the ethyl salt of mono-chlor-formic 
acid, Cl.COOH; and, properly speaking, should be called ethyl 
chlor-formate. 

Carbon disulphide acts very much like carbon dioxide towards 
alkalies and alcohols, and thus a number of ether acids and 
ethereal salts containing sulphur can be made. Thus, when 
carbon disulphide is added to a solution of caustic potash in 

OC TT 

alcohol, a potassium salt of the formula CS < ' 2 5 is formed. 

This is called potassium xanthogenate. The free xanthogenic 
acid is very unstable, breaking up into alcohol and carbon 
disulphide. The formation of the salt is represented by the 
following equation : — 

CS 2 + KOH + C 2 H 5 OH = CS < °J^* + H 2 0. 

A similar salt made from ordinary amyl alcohol has been used 
for the purpose of destroying phylloxera, the insect, which is so 
destructive to grape-vines, particularly in the wine districts of 
France. 



General methods for the preparation of hydroxy-acids. The 
methods available for making the hydroxy-acids are modifica- 
tions of those used for making alcohols and acids. 

Starting with a mon-acid alcohol, we can make a hydroxy- 
acid b}' the same methods which we used in making an acid 
from a hydrocarbon. Suppose, for example, that we are to 
make acetic acid from marsh gas. The reactions which we 
make use of are : (1) the preparation of a halogen derivative ; 
(2) conversion of the halogen derivative into the cyanogen 



158 DERIVATIVES OF THE PARAFFINS. 

derivative ; and (3) conversion of the cyanogen derivative into 
the acid. We describe the results of these operations by saying 
that we have introduced carboxyl. By similar operations we 
can introduce carboxyl into methyl alcohol, and the product is 
hydroxy-acetic acid. 

It is, however, generally better to start with an acid, and 
introduce hydroxyl. This can be done in several ways : — 

1. By treating a halogen derivative of an acid with water or 
silver hydroxide : — 

CH '<C0 2 H +HH ° = CH *<c? 2 H + HBr - 

Brom-acetic acid. 

2. By treating an amido derivative of an acid with nitrous 
acid (see page 98) : — 

CH *<™'u + HN ° 2 = CH ^<mn + N * + ^°' 

Amido-acetic acid. 

3. By treating a sulphonic-acid derivative of an acid with 
caustic potash : — 

CH2< caH H + K0H = CH2 < co h + KHS ° 3 ' 

Sulpho-acetic acid. 

The first two of these reactions have been described and men- 
tioned as affording methods for the introduction of hydroxyl 
into hydrocarbons. It will be seen that the only difference 
between the reactions used in making alcohols and those used 
in making hydroxy-acids is that in one case we start with the 
hydrocarbons, while in the other we start with the acids. 

Glycolic acid, hydroxy-acetic acid, oxy-acetic acid, 

G 2 T£±oJ = CH 2 < rL. ]. — Glvcolic acid is found in nature in 
V G0 2 H/ 

unripe grapes, and in the leaves of the wild grape (Ampelopsis 
hederacea) . 



GLYCOLIC ACID, ETC. 159 

It can be made from glycocoll, which is amicloacetic acid (see 
reaction 2, above), from brom- or chlor-acetic acid and water 
(see reaction 1, above), and by the oxidation of glycol : — 

CH 2 OH C0 9 H 

| +0 2 = | -f H 2 0. 

CH 2 OH CH 2 OH 

Glycol. Glycolic acid. 

This consists in transforming one of the primary alcohol groups, 
CH 2 OH, contained in glycol into carboxyl. (What would be 
formed b} T conversion of both the primary alcohol groups of 
glycol into carboxyl ?) It can also be made by careful oxida- 
tion of ethyl alcohol with nitric acid. For this purpose a 
mixture of alcohol and nitric acid is allowed to stand until no 
further action takes place. 

Glycolic acid forms crystals which are easily soluble in water, 
alcohol, and ether. 

As an acid, glycolic acid forms a series of salts with metals, 
and ethereal salts with alcohol radicals. The latter, of which 
ethyl glycolate may be taken as an example, can be made by 
means of one of the reactions usually employed for making 
ethereal salts ; for example, by treating silver glycolate with 
ethyl iodide : — 

C0 2 Ag C0 2 C 2 H 5 

In this reaction, as well as in the formation of salts of glycolic 
acid, the alcoholic hydroxyl remains unchanged. 

As an alcohol, glycolic acid forms ethers of which ethyl- 

gly colic acid, CH 2 < ~ * TT 5 , may serve as an example. It will be 
C0 2 H 

seen that this is isomeric with ethyl glycolate. But while the 
latter has alcoholic properties, the former has acid properties. 
Ethyl glycolate is a liquid which boils at 1G0°. Ethyl-glycolic 
acid is a liquid which boils at 206° to 207°. Finally, as an 
alcohol, glycolic acid forms ethereal salts, of which acetyl- 
gly colic acid may serve as an example. This is glycolic acid 



160 DERIVATIVES OF THE PARAFFINS. 



in which the hydrogen of the hydroxyl is replaced by acetyl, 

O C II o 
CH 2 < _ 2 " 3 , bearing, as will be seen, the same relation to 

glycolic acid and acetic acid that ethyl acetate, C 2 H 3 .O.C 2 H 3 0. 
bears to alcohol and acetic acid. 

Glycolic acid and some of the other acids of the series lose 
water when heated, and yield peculiar anhydrides. The prod- 
uct obtained from glycolic acid is called glycolide. It has 
neither acid nor alcoholic properties, and is, therefore, be- 
lieved to be derived from glycolic acid as represented in this 
equation : — 

nw CH 2 - O - CO 

2CH2< rooH= ! ' +2H2 °' 

COOH co _ _ CH2 

Glycolide. 

Glycolide is insoluble in cold water. When boiled for a long 
time with water, it is converted into glycolic acid. 

Lactic acids, hydroxy-propionic acids, oxy-propionic 

acids, C 3 H 6 3 ( = C 2 H 4 < ro „)> — In speaking of proprionic 

acid, it was pointed out that two series of substitution-products 
of the acid are known, which are designated as the a- and j3- 
series. Accordingly we should expect to find two hydroxy- 
propionic acids, the a- and the /?-acid. Two lactic acids 
have been known for a long time. One of these is ordinary 
lactic acid; the other a variety which is found in flesh, and 
hence called sarco-lactic acid. But, strange to say, a thorough 
investigation of these two acids has proved that both must be 
represented by the same structural formula, as both conduct 
themselves in exactly the same wa} T towards reagents. Further, 
two other hydroxy-propionic acids are certainly known. The 
facts then are these : four acids are known, all of which are 
hydroxy-propionic acids. Our theory enables us to foretell the 
existence of only two. Before discussing this apparent dis- 
crepancy let us briefly study the acids themselves. 



LACTIC ACIDS. 161 

1. Lactic acid, inactive ethylidene-lactic acid, a-hy- 

droxy-propionic acid, CH 3 .CH<^ — Lactic acid is 

OU2M 

made by the fermentation of sugar, as has already been 

described under Butyric Acid (which see). The process is 

carried out best by dissolving cane sugar and a little tartaric 

acid in water ; then adding putrid cheese, milk, and zinc 

carbonates, the object of which is to prevent the solution from 

becoming acid, as the presence of free acid is fatal to the 

ferment. Lactic acid can also be made by fermentation of 

sugar of milk, and is hence contained in sour milk ; bj T boiling 

a-chlor-propionic acid with alkalies, — 

CH 8 .CH<^ H + KOH a =CH 8 .CH<^ H + KCl; 

and by treating alanine (a-amido-propionic acid) with nitrous 
acid, — 

CH 3 . CH < NHs + HNO, = CH 3 . CH < 0H + N 2 + H 2 0. 
C0 2 H " 3 C0 2 H 

Lactic acid is a thick liquid which mixes with water and with 
alcohol in all proportions. 

Treated with hydriodic acid, it is reduced to propionic acid. 
Treated with hydrobromic acid, it yields a-brom-propionic acid. 

2. Sarco-lactic acid, dextro-ethylidene-lactic acid, 
CH 3 .CH< — This acid occurs in the liquids expressed 

from meat. It is therefore contained in "extract of meat," 
and can be obtained most readily from this source. 

Its properties are, for the most part, like those of inactive 
lactic acid, and its conduct towards reagents is in all respects 
the same. Its salts are somewhat more easily soluble than 
those of ordinary inactive lactic acid. The chief difference 
between the two is observed in the action towards polarized 
light. Dextro-lactic acid turns the plane of polarization to the 



162 DERIVATIVES OE THE PARAFFINS. 

right. Its salts are all levo-rotatory. On the other hand, 
neither inactive lactic acid nor its salts exert any action upon 
polarized light. 1 

OH 

3. Levo-lactic acid, CH 3 .CH< co H - — A third variety 

of ethylidene-lactic acid, which turns the plane of polarization to 
the left, is formed from cane sugar by the action of a certain 
ferment found in a spring-water. Both the dextro- and the 
levo-acids can also be obtained from the ordinary inactive variety 
by fractional crystallization of the strychnine salts. The rela- 
tions between these three acids are of the same kind as those 
existing between the three varieties of tartaric acid. 

4. Hydracrylic acid, ) CH 2 OH 

p-Hydroxy-propionic acid, J CH 2 . C0 2 H 
Hydracrylic acid is made by boiling /3-iodo-propionic acid with 
water or silver oxide and water : — 

CH 2 I CHo.OH 

| +HHO= | +HI. 

CH 2 .C0 2 H CH 2 .C0 2 H 

CH 2 
It is made also by starting with ethylene, | . When this 

CH 2 

hydrocarbon is treated with hypochlorous acid, HOC1, it is con- 

CH 2 C1 
verted into ethylene-chlorhydrine, | (which see). By 

CH 2 OH 

replacing the chlorine with cyanogen, and boiling the cyan- 

CH 2 OH 
hydrine, | , thus obtained, with an alkali, hydracrylic acid 

CH 2 CN 
is obtained. 

These reactions clearly show that hydracrylic acid is an 

ethylene compound, and, as it is made from /Modo-propionic 

1 See active and inactive amyl alcohols, p. 126. 



ETHYLENE-LACTlC ACID. 163 

acid by replacing the iodine with hydroxyl, it follows further 
that the /2- substitution-products of propionic acid are ethylene 
products, and that the a-products are ethylidene products (see 
p. 131). 

Hydracrylic acid is a syrup. Its salts differ markedly from 
those of the inactive and active lactic acids. When heated, it 
loses water and is transformed into acrylic acid, CH 2 .CH.C0 2 H 
(which see). 

The difference in conduct between ethylidene-lactic acid and 
ethylene-lactic acid, when heated, is interesting and suggestive. 
When ethylidene-lactic acid is heated, both its acid and alco- 
holic properties are destroyed, both the alcoholic and acid 
hydroxy Is taking part in the reaction. Whereas, when ethyl- 
ene-lactic acid is heated, only the alcoholic properties are 
destroyed, the carboxyl remaining intact. 

There are then more hydroxy-propionic acids known than our 
theory can account for. Other cases of this kind are known, 
and one very marked and especially interesting one will be 
referred to when tartaric acid is considered. It will be shown 
that just as there are two active lactic acids and an inactive one, 
so there are two active tartaric acids and an inactive one, which 
conduct themselves in the same way towards reagents, and 
must hence be represented by the same structural formula. 

Apparently we have here to deal with a new kind of isome- 
rism. Bodies may conduct themselves chemically in exactly 
the same way, and yet differ in -some of their physical proper- 
ties, as in their action towards polarized light. To distinguish 
this kind of isomerism from ordinary chemical isomerism it is 
called physical isomerism. 

An ingenious hypothesis has been put forward by way of 
explanation of that particular kind of physical isomerism which 
shows itself in the action of compounds upon polarized light. 
It must be remembered that our ordinary formulas have nothing 
whatever to do with the relations of the atoms and groups in 



164 



DERIVATIVES OF THE PARAFFINS. 



space. They indicate chemical relations which are discovered 
by a study of chemical reactions. 

Let us suppose that in a carbon compound one carbon atom 
is situated at the centre of a tetrahedron, and that the four 
atoms or groups which it holds in combination are at the angles 
of the tetrahedron, as represented in Fig. 10. 

If these groups are all different in kind, and only in this 
case, it is possible to arrange them in two waj^s with reference 
to the carbon atom. The difference between the two arrange- 

R x Ri 





ments is that which is observed between either one and its 
reflection in a mirror. Imperfectly the second arrangement 
of the figure above represented is shown in Fig. 11. 

A carbon atom, in combination with four different kinds of 
atoms or groups, is called an asymmetrical carbon atom. When- 
ever, therefore, a compound contains an asymmetrical carbon 
atom, there are two possible arrangements of its parts in space 
which correspond to the two complementary tetrahedrons, viz., 
the right-handed and the left-handed tetrahedron. 

In ethylidene lactic acid there is an asymmetrical carbon atom, 
as shown by the ordinary formula, which may be written thus : 



CH 5 



C — OH, the central carbon atom appearing in combination 

CO,H 
with (1) hydrogen, (2) hydroxyl, (3) carboxyl, and (4) methyl. 



HYDHOXY-ACIDS, C n H 2a 4 . 165 

Hence, according to the hypothesis just stated, there ought to 
be two possible arrangements of the parts of a compound con- 
taining this group, one corresponding to the right-handed tetra- 
hedron, the other to the left-handed tetrahedron. Both would 
be ethylidene-lactic acids. The inactive variety is formed by 
the combination of the two active varieties, and must, therefore, 
have a greater molecular weight than these. 

The branch of chemistry which has to deal with the kind of 
isomerism just referred to is called stereo-chemistry. 

We have seen that the sulphonic acids and carbonic acids are 
analogous : that, for example, methyl-sulphonic acid, CH 3 .SQ 3 H, 
is analogous to methyl-carbonic or acetic acid, CH 3 .C0 2 H. Now, 
just as the hyclroxy-acids above considered are derived from the 
carbonic acids by the introduction of hydroxyl, so we may have 
a series of hydroxy-acids derived in a similar way from the sul- 
phonic acids. Only one such acid is well known. It is — 

OH 

Isethionic acid, C 2 H 4 < SOH > also called hydroxy-ethyl- 

sulpJionic acid. In composition it is analogous to the hydroxy- 
propionic acids. It is prepared by passing sulphur trioxide into 
w.ell cooled alcohol or ether. 

Hydroxy-acids, C n H2 a 4 . 

The acids just considered are called monohydroxy-monobasic 
acids. Similarly, there are dihydroxy -monobasic acids, which 
are regarded as derived from the monohydroxy-acids by the 
introduction of a second hydroxyl. Thus, if into lactic acid, 

PC) it 

CH 3 .CK< OH 2 , a second hydroxyl is introduced, the product 

CH 2 .OH 
I 
would have the formula CH.OH. This is the best known 

I 
C0 2 H 

dihydroxy-monobasic acid of the paraffin series. 



166 DERIVATIVES OF THE PARAFFINS. 

/ CH 2 OHv 

Glyceric acid, C 3 H 6 oJ = CHOH . — This acid has been 

V C0 2 H / 
referred to as the first product of the oxidation of glycerin. It 
is prepared by allowing glycerin and nitric acid to stand together 
at the ordinary temperature for some time, and then heating on 
the water-bath. It can also be made by treating one of the 
chlor-lactic acids with water. 

An optically active variety of glyceric acid has been obtained 
from the inactive variety. 

Glyceric acid is a thick syrup which mixes with water and 
alcohol. When treated with very concentrated hydriodic acid, 
it is converted into /?-iodo-propionic acid. This conversion 
involves two reactions : — 

CH 2 OH CH 2 I 

I I 

(1) CHOH + HI = CHOH + H 2 0, and 

I I 

C0 2 H C0 2 H 

CH 2 I CH 2 I 

I I 

(2) CHOH + 2 HI = CH 9 + H 2 + 21. 

I I 

C0 2 H C0 2 H 



Hydroxy-acids, C n H 2n _ 2 5 . 

The acids included uuder this head are monohydroxy -dibasic 
acids. They bear the same relation to the dibasic acids of the 
oxalic acid series that the simplest hydroxy-acids bear to the 
members of the formic acid series. The principal members of 
this series, and the only ones which will be considered, are 
tartronic acid and malic acid. 



MALIC ACID. 167 

Tartronic acid, C 3 H 4 5 (= 0H( OH )< qq 2 ^)- — This acid 
is prepared by an indirect method from tartaric acid. It can 
be made, — 

(1) By boiling brom-malonic acid with silver oxide and 
water : — 

CHBr<^H + AgQH = CH(OH)< COg + AgBr . 

(2) By treating brom-cyan-acetic acid with caustic potash : — 

CHBr < 5? „ + 2 KOH + H 2 
L/(J 2 H 

= CH(OH) <^ 2 ^ + NH 3 + KBr. 

UU 2 xi 

Tartronic acid is a solid which crystallizes in prismatic crystals. 
It is easily soluble in water, alcohol, and ether. It melts at 
182°. At 155° it gives off carbon dioxide and water, and is 
converted into glycolide (which see) : — 

(1) CH(OH)<jgH =CH 2 <£JJ H + C0 2 . 

Glycolic acid. 

nw CH 9 - O - CO 

(2) 2CH 2 <^ nH = I I +2H 2 0. 

UUUhL CQ _ q _ CHj 

Glycolide. 

Note for Student. — Compare reaction (1) with that which takes 
place when iso-succinic acid is heated, and note the analogy. 

Hydroxy-succinic acids, C;H 6 5 (=C 2 H 3 (OH)<£Q 2 :?y — 

Three hydroxy-succinic acids have been described, the principal 
one being ordinary malic acid. 

/ CH(OH).C0 2 H\ 
Malic acid, 4 H 6 O 5 = I ). — This acid is very 

V CH 2 .C0 2 H / 
widely distributed in the vegetable kingdom, as in the berries 

of the mountain ash, in apples, cherries, etc. 

It is best prepared from the berries of the mountain ash 



168 DERIVATIVES OF THE PARAFFINS. 

which have not quite reached ripeness. The berries are pressed 
and boiled with milk of lime. The acid passes into solution as 
the calcium salt, and this is purified by crystallization. 

It can also be made by treating aspartic acid, which is amido- 

CO TT 

succinic acid, C 2 H 3 (NH 2 ) < * TT , with nitrous acid, and by treat- 
ed U 2 H 

ing tartaric acid with hydriodic acid. This latter reaction will 
be explained when tartaric acid is considered . Tartaric and 
malic acids are closely related to each other, and both are 
related to succinic acid, as will appear from the reactions. 

Malic acid is a solid substance which ciystallizes with diffi- 
cult} 7 . It is very easily soluble in water and in alcohol. Its 
solutions turn the plane of polarization to the right or to the left, 
according to the concentration. 

When heated it loses water and yields either fumaric or 
maleic acid (which see) , according to the temperature. These 
acids are isomeric, and both are represented by the formula 

CO TT 

C 2 H 2 < ro 2 H - The reaction mentioned is represented by the 
following equation : — 

c 2 h s (oh)<^h = c 2 h 2 <co : h + H2 o. 



Malic acid. 



Fumaric or 
malei'c acid. 



Note for Student. — Compare this reaction with that which takes 
place when hydracrylic acid is heated, and note the analogy. 

When treated with hydriodic acid, malic acid is reduced to 
succinic acid. 

Note for Student. — Compare this reaction with the conduct of 
lactic and glyceric acids when treated with hydriodic acid. 

Treated with hydrobromic acid, malic acid is converted into 
mono-brom-succinic acid. 

The reactions just described show clearly that malic acid is 
hydroxy-succinic acid. Nevertheless, if hydroxy-succinic acid 
is made by treating brom-succinic acid with silver oxide and 



INACTIVE MALIC ACID. 169 

water, the product is not identical with ordinary malic acid, 
though the two resemble each other ver} 7 closely. The acid 
thus obtained is — 

Inactive malic acid, C 2 H 3 (OH) < «X 2 t** — Inactive malic 

OvJ 2 H 

acid can be made not only by the method first mentioned, but 
by several others, which indicate that the relation between it 
and succinic acid is that expressed in the formula given. It, 
like ordinary malic acid, is unquestionably a hydroxy-succinic 
acid, and both are derived from ordinary succinic acid. 

Other reactions for the preparation of inactive malic acid 
are, — 

(1) By treating dichlor-propionic acid with potassium cyanide, 
and boiling the product with caustic potash : — 

CH 2 C1.CHC1.C0 2 H + KCN 
CH 2 CN 
= I +KC1; 

CHC1.C0 2 H 

CH CN 
and | +2 KOH + H 2 

CHC1.C0 2 H 

CH 9 .C0 2 K 
= | 4- KC1 + NH 3 . 

CH(OH).C0 2 H 

(2) By heating fumaric acid with water : — 

cA< co:H +H2 °= cA(OH)< co:H ;a,id 

(3) By reduction of racemic acid with hydriodic acid. Ea- 
cemic acid has the same composition as tartaric acid. The 
latter, when treated with hydriodic acid, yields active malic 
acid. 

The properties of inactive malic acid are very much like 
those of active malic acid. As regards their chemical conduct 



170 DERIVATIVES OF THE PARAFFINS. 

they are almost identical. The principal difference between 
them is observed in their conduct towards polarized light. 
They present a new case of physical isomerism of the same 
kind as that referred to in connection with the lactic acids 
(which see). 

Dextro-malic acid. — Inactive malic acid bears the same 
relation to two active acids that inactive lactic acid bears to the 
two active varieties of that acid. When the cinchonine salt of 
inactive malic acid is subjected to fractional crystallization, two 
different salts are obtained. One of these is derived from 
ordinary levo -malic acid, while the other is derived from the 
isomeric dextro-malic acid. 

Hydroxy- acids, C n H 2n _ 2 6 . 

These are di-hydroxy -dibasic acids. The chief members of 
the group are mesoxalic acid and the different modifications 
of tartaric acid. 

Mesoxalic acid, C 3 H 4 o/= C(OH) 2 < qqj||j\ — ™ s acid 

is obtained by indirect and rather complicated reactions from 
uric acid (which see). It has been made also by boiling di- 
brom-malonic acid with baryta-water. 

Note for Student. — Explain this reaction. 

The acid forms deliquescent needles. When boiled it loses 
carbon dioxide and water, and glyoxylic acid, which is an alde- 
hyde and acid related to oxalic acid, is formed : — 



C0 2 H 



CHO 
C(OH) 2 <^ 2 " = | + C0 2 + H 2 0. 

CU2±1 C0 2 H 

Grlyoxylic acid. 



This acid affords an example of a very rare condition ; viz., 
the existence of a compound in which two hydroxyls are in 
combination with one and the &ame carbon atom. 



TARTARIC ACID. 171 

Di-hydroxy-succinic acids, C 4 H 6 6 ( = C 2 H 2 (OH) 2 < co 2 H )• 

0H(OH).CO 2 H 
1 Tartaric acid, I . — Ordinary tartaric acid 

0H(OH).CO 2 H 

occurs very widely distributed in fruits, sometimes free, some- 
times in the form of the potassium or calcium salt; as, for 
example, in grapes, berries of the mountain ash, potatoes, 
cucumbers, etc., etc. 

It can be made by the following methods : — 

(1) By oxidizing sugar of milk with nitric acid ; 

(2) Also by oxidizing cane sugar, starch, glucose, and other 
similar substances. 

Tartaric acid is prepared from "tartar," which is impure 
acid potassium tartrate. When grape juice ferments this salt 
is deposited. It is purified by crystallization, converted into 
the calcium salt by treating it with chalk, and the calcium salt 
then decomposed b} T means of sulphuric acid. 

The acid crystallizes in large monoclinic prisms, which are 
easily soluble in water and alcohol. It melts at 135°. Its 
solution turns the plane of polarization to the right. 

Treated with hydriodic acid, tartaric acid yields first malic 
acid and then ordinary succinic acid : — 

(1) C 2 H 2 (OH) 2 <[gH + 2HI 

= C 2 H 3 (OH)<gVj + H 2 + I 2 ; 

Malic acid. 

(2) C 2 H 3 (OH) <^J+!HI 

Succinic acid. 

While malic acid is mono-hydroxy-succinic acid, ordinary 
tartaric acid appears to be di-hydroxy-succinic acid. But, just 






172 DERIVATIVES OF THE PARAFFINS. 

as we found that the malic acid prepared from mono-brom-suc- 
cinic acid is optically inactive, and therefore different from 
natural, active malic acid, so too it has been found that the 
tartaric acid prepared from di-brom-succinic acid is optically 
inactive, and therefore different from ordinary tartaric acid. 
The relations between the natural and the artificial acids will 
be considered more fully below. 

Tartrates. Among the salts the following may be mentioned 
specially : — 

Mono-potassium tartrate, KH.C 4 H 4 6 . This is the chief 
constituent of tartar. In pure form, as used in medicine, it is 
known as cream of tartar. 

Sodium-potassium tartrate, KNa.C 4 H 4 6 + 4 H 2 0. This 
salt crystallizes very beautifully. It is known as Rochelle salt 
or Seignette salt. 

Calcium tartrate, Ca.C 4 H 4 6 -}- 4 H 2 0. This salt occurs in 
senna leaves and in grapes. It forms a crystalline powder or 
rhombic octahedrons. 

Potassium -antimonyl tartrate, K ( SbO ) . C 4 H 4 6 -f- i H 2 0. 
This is known as tartar emetic. It is prepared by digesting 
antimonic oxide with mono-potassium tartrate. It crystallizes 
in rhombic octahedrons. It loses its water of crystallization at 
100°, and at 200 to 220° is converted into an antimony potas- 
sium salt of the formula KSb.C 4 H 2 6 . 

2. Racemic acid, C 4 H 6 6 + H 2 0. — Racemic acid occurs, 
together with tartaric acid, in many kinds of grapes, and, on 
recrystallizing the crude tartar, acid potassium racemate, being 
more soluble than the tartrate, remains in the mother liquors. 
Racemic acid is formed by boiling ordinary tartaric acid with 
water, or with hydrochloric acid. If tartaric acid is heated 
with water in sealed tubes at 175°, it is almost completely 
transformed into racemic acid. It is formed further by oxida- 
tion of dulcite, mannite, cane sugar, gum, etc., with nitric 
acid. It, together with a third variety of tartaric acid, known as 



RACEMIC ACID. 173 

inactive tartaric acid, is formed when dibrom-succinic acid is 
treated ivith silver oxide and water. 

Kacemic acid differs from tartaric acid in many ways. It 
crystallizes differently, and contains water of crystallization. 
It is less soluble than tartaric acid. It produces precipitates 
in solutions of lime salts, while tartaric acid does not. Racemic 
acid is optically inactive, while tartaric acid is dextro-rotatory. 
On the other hand, racemic and tartaric acids conduct them- 
selves towards most reagents exactly alike. 

The relations between racemic and tartaric acid are the same 
as those which have already been referred to as existing between 
inactive malic acid and dextro-malic acid, and between inactive 
lactic and dextro-lactic acid. This case is, however, of special 
interest, as it was the first one of the kind studied. The relations 
were discovered by means of the experiment described below. 

When a solution of ammonium-sodium racemate, 

(NH 4 )Na.C 4 H 4 6 , 

is allowed to evaporate spontaneously, beautiful large crystals 
are deposited. On examining these carefully, they are found 
to be of two kinds. On the crystals of one kind certain hemi- 
hedral faces are developed, while on the crystals of the other 
kind the complementary hemihedral faces are developed ; so 
that if a crystal of one kind is placed in front of a mirror, 
its reflection will represent the arrangement of the hemihedral 
faces met with on a crystal of the other kind. The crystals 
can be separated into right-handed, or those which have the 
right-handed hemihedral faces, and left-handed, or those which 
have the left-handed hemihedral faces. 

On separating t the acid from the right-handed crystals it is 
found to be ordinary dextro-rotatory tartaric acid; while the 
acid from the left-handed crystals is an isomeric substance 
called Icevo-rotatory tartaric acid. When these two varieties 
of tartaric acid are brought together in solution, they unite, the 
action being attended by an elevation of temperature, and the 
result is racemic acid. 



174 DERIVATIVES OF THE PARAFFINS. 

We see thus that the inactive racemic acid consists of two 
optically active substances in combination, one of which, ordinary 
tartaric acid, is dextro-rotatory, and the other levo-rotatory. 

As has already been stated, both inactive malic acid and 
inactive lactic acid have been resolved into two active varieties, 
one of which is dextro-rotatory, and the other levo-rotatoiy. 

Inactive tartaric acid is very similar to racemic acid. 
It is formed together with racemic acid by treating dibrom- 
succinic acid with silver oxide and water. The inactivity of 
this acid is believed to be due to a different arrangement of the 
groups about the two asymmetrical carbon atoms. 

Hydroxy- acids , C n H 2 n _ 4 7 . 

These are mono-hydroxy-tribasic acids. Citric acid is the 
only one known. 

/ c C0 2 H x 

Citric acid, 6 H 8 O 7 + H 2 0( = C 3 H 4 (OH) 5 C0 2 H ). — Citric 

V ( CCW 

acid, like malic and tartaric acids, is very widely distributed in 
nature in many varieties of fruit, especially in lemons, in which 
it occurs in the free condition. It is found in currants, whortle- 
berries, raspberries, gooseberries, etc., etc. 

It is prepared from lemon juice. This is allowed to ferment 
and is then treated with lime. The lime salt thus obtained 
in the form of a precipitate, is collected, and decomposed with 
sulphuric acid. 100 parts of lemons yield 5 J parts of the acid. 

Citric acid crystallizes in rhombic prisms which are veiy easily 
soluble in water. The crystallized acid melts at 100°, the 
anhydrous at 153° to 154°. Heated to 175° it loses water and 
yields aconitic acid (which see) : — 

rC0 2 H rC0 2 H 

C 3 H 4 (OH) ] C0 2 H = C 3 H 3 ] C0 2 H + H 2 0. 
(C0 2 H IC0 2 H 

Aconitic acid. 



CITRIC ACID. 175 

Note for Student. — Compare with formation of acrylic from 
hydracrylic acid; and of maleic and fumaric acids from malic acid. 

Aconitic acid takes up hydrogen, and is transformed into tri- 
earballylic acid (which see) . Thus a clear connection between 
tricarballylic acid and citric acid is traced, the latter appearing 
as hydroxy-tricarballylic acid. Citric acid has been made arti- 
ficially by a somewhat complicated method. 

When subjected to dry distillation, citric acid loses both water 

CO H 
and carbon dioxide, and }ields citraconic acid, C 3 H 4 < 2 , 

C0 2 H 

(which see) ; if heated with water or dilute sulphuric acid to 

CO H 

160° it yields itaconic acid, C 3 H 4 < 2 , (which see). 

C 3 H 4 (OH) ] C0 2 H = C^J °°*E + H 2 + C0 2 . 
(C0 2 H CC ° 2H 

Citraconic or ita- 
conic acid. 

Note for Student. — What relation, as far as composition is 

f CO IT 
concerned, do these two acids of the formula C 3 H 4 -{ rA 2 bear to 

l. C0 2 tL 

fumaric and maleic acids? By distillation of what acid are the two 

latter formed? 

Citrates. A few of the salts of citric acid are mentioned : — 

Mono-potassium citrate, KH 2 .C 6 H 5 7 -f- 2 H 2 ; 

Di-potassium citrate, K 2 H.C 6 H 5 7 ; 

Tri-potassium citrate, K 3 .C G H 5 7 -f- H 2 0. All these potas- 
sium salts are easily soluble in water. They are made by 
mixing citric acid and potassium carbonate in the right pro- 
portions. 

Calcium citrate, Ca 3 (C 6 H 5 7 ) 2 + 4 H 2 0. This salt is formed 
by mixing a citrate of an alkali with calcium chloride. It is 
more easily soluble in cold than in hot water ; hence boiling 
causes a precipitate in dilute solutions. 

Magnesium citrate, Mg 3 (C 6 H 5 7 ) 2 -f- 14 H 2 0. This is made by 
dissolving magnesia in citric acid. It is used in medicine. 



176 DERIVATIVES OF THE PARAFFINS. 

Hydroxy- acids, C n H 2n _ 2 8 . 

There are two acids to be considered under this head. They 
are isomeric, and both are tetra-hydroxy-dibasic. 

Saccharic acid, C 6 H 10 o/= C 4 H 4 (OH) 4 <°° 2 :|).— Saccharic 

acid is formed by the oxidation of cane sugar, glucose, or sugar 
of milk with nitric acid. 

To prepare it, it is best to treat ordinary sugar with dilute 
nitric acid. Oxalic acid is formed at the same time. 

It is an amorphous mass, which becomes solid only with 
difficulty. When treated with hydriodic acid it is converted 
into adipic acid, a member of the oxalic acid series (see table, 
page 142) : — 

C 4 H 4 (OH) 4 < jgg + 8 HI = C 4 H 8 < jg^j + 4 H 2 + 8 I. 

Saccharic acid. Adipic acid. 

Note foe Student. — What relations exist between hexane, man- 
nite, adipic acid, aud saccharic acid? 

Mucic acid, C 6 H 10 O 8 (^ C 4 H 4 (OH) 4 < qoh)' _ Mudc add 
is formed by oxidizing sugar of milk, the gums, or dulcite, with 
nitric acid. 

It is best prepared by boiling sugar of milk with ordinary 
nitric acid. Oxalic and tartaric acids are formed at the same 
time. 

It is a crystalline powder which is very difficultly soluble in 
cold water. Hydriodic acid converts it into adipic acid (see 
above, under Saccharic Acid). 



CHAPTER XI. 
CARBOHYDRATES. 

Among the mixed compounds are the important substances 
commonly known as carbohydrates. This name was originally 
given to them because they consist of carbon in combination 
with hydrogen and oxygen, which two elements are present 
in the proportion to form water, as shown in the formulas, for 
glucose, C 6 H 12 0«3, starch, C 6 H ]0 O 5 , etc. In view of recent dis- 
coveries the name is no longer strictly accurate, as some sub- 
stances belonging to this group are now known that do not 
contain hydrogen and oxygen in the proportion to form water. 
Such a substance, for example, is rhamnose, C 6 H 12 5 . The 
name carbohydrate has, however, been used so long that it 
would be difficult to supplant it. 

The carbohydrates may be conveniently classified under three 
heads. These are : — 

1. Monosaccharides or simple sugars. 

Examples of these are glucose, fructose, arabinose, and 
mannose. 

2. Polysaccharides or complex sugars. 

Examples are cane sugar, sugar of milk, maltose, and 
isomaltose. 

3. Polysaccharides, not resembling sugars. 
Examples are cellulose, starch, and gums. 

The monosaccharides are the simplest carbohydrates. Those 
that are best known have the composition, C 6 H 12 6 , and are 
related to the hex-acid alcohols, sorbite and inannite, C 6 H s (OH) 6 . 
There are, however, simpler ones, such as arabinose, C 5 H 10 O 5 , 
erythrose, C 4 H 8 4 , and glycerose, C 3 H 6 3 ; and some that are 



178 CARBOHYDRATES. 

more complex, as heptose, C 7 H 14 7 , octose, C 8 H 16 8 , and nonose, 

C 9 H 18 9 . The monosaccharides, therefore, fall into classes 
which are called trioses, tetroses, pentoses, hexoses, etc., accord- 
ing to the number of oxygen atoms contained in them. 

By methods which will be explained below, it has been shown 
that the monosaccharides or simple sugars are aldehyde- alcohols 
or ketone-alcohols. 

1. Monosaccharides. 
A. Trioses and Tetroses. 

Glycerose, C 3 H 6 03. — This sugar deserves special mention 
as being the simplest member of the group of monosaccharides, 
and as having been obtained artificially. It is formed by treat- 
ing glycerin with mild oxidizing agents, as, for example, bromine 
and sodium hydroxide. It is a mixture of glyceric aldehyde 
and dioxyacetone, the relations of which to glycerin are shown 
by the following formulas : — 

CH 2 OH CHO CH 2 OH 

I I I 

CHOH CHOH CO 

I I I 

CH 2 OH CH 2 OH CH 2 OH 

Glycerin. Glyceric aldehyde. Dioxy-acetone. 

Glycerose is a syrup that undergoes fermentation and re- 
duces alkaline solutions of copper salts, acting thus like many 
of the sugars, as will be shown. 

Erythose, C 4 H 8 4 , has been obtained from erythrite in the 
same way that glycerose is obtained from glycerin. 

B. Pentoses. 

Arabinoses, C 5 Hi O 5 . — Ordinary arabinose is obtained 
from cherry gum by boiling with dilute sulphuric acid. This 
variety is called levo-arabinose on account of its relation to 



GLUCOSE. 179 

levo-glucose and levo-mannose, although it turns the plane of 
polarization to the right. Dextro-arabinose 1 and inactive arabi- 
nose have also been obtained, the latter by combination of the 
levo and dextro varieties. 

Xylose, C5H10O5, is obtained from wood gum by boiling 
with dilute acids. 

Rhamnose, C 6 Hi 2 05, has been obtained by the breaking 
down of a number of natural substances, such as quercitrin. It 
has been shown to be a methyl derivative of a pentose, and is 
therefore to be represented by the formula CH 3 . C 5 H 9 5 . 

C. Hexoses. 

Glucose, grape sugar (dextrose), C 6 Hi 2 6 . — Glucose 
occurs very widely distributed in the vegetable kingdom, 
especially in sweet fruits, in which it is found together with an 
equivalent quantity of fructose or fruit sugar. It is also found 
in honey, together with fructose ; and, further, in the blood, in 
the liver, and in the urine ; and in the disease Diabetes mellitus, 
the quantity contained in the urine is largely increased, reaching 
as high as 8 to 10 per cent. 

Glucose is formed from several of the carbohydrates of the 
formulas C 12 H 22 O n and C 6 H 10 O 5 , by boiling with dilute mineral 
acids, or by the action of ferments. The formation from cane 
sugar takes place according to this equation, equivalent quanti- 
ties of glucose and fructose being formed : — 

C 12 H2 2 O n + H 2 = C 6 H 12 6 -f- C 6 H 12 6 . 

Cane sugar. G-lucose. Fructose. 

Starch, cellulose, and dextrin yield glucose according to this 
equation : — 

C 6 H 10 O 5 -|- H 2 = C 6 H 12 6 . 

1 Instead of using the prefixes dextro-, levo-, and the word inactive, it is customary 
to use the letters d-, 1-, and i-. Thus the three arabinoses are called respectively d-ara- 
binose, Z-arabinose, and i-arabinose. 



180 CARBOHYDRATES. 

Finally, glucose occurs in nature, in combination with a 
number of carbon compounds, in the so-called glucosides. These 
break up easily when treated with dilute mineral acids or fer- 
ments, and yield glucose as one of the products (see Glucosides). 
Examples of the glucosides are amygdalin, aesculin, salicin, etc. 

Glucose is prepared on the large scale from corn starch in 
the United States, and from potato starch in Germany. The 
transformation is usually effected by boiling with dilute sul- 
phuric acid. The excess of acid is removed by treating the 
solutions with chalk, and filtering. The filtered solutions are 
evaporated down either to a syrupy consistency, and sent into 
the market under the names " glucose," " mixing syrup," etc., 
or to dryness, the solid product being known in commerce as 
"grape sugar." By evaporating the solutions down to such 
a concentration that they contain from 12 to 15 per cent of 
glucose, crystals are formed which closely resemble those of 
cane sugar. They consist of anhydrous grape sugar. Their 
formation is facilitated by adding a little of the crystallized 
substance to the concentrated solutions. 

If in the treatment of starch with sulphuric acid the trans- 
formation is not complete, and this is usually the case, the 
product is a mixture of glucose, maltose, and dextrin. The 
longer the action continues, the larger the percentage of glucose. 

Glucose crystallizes from concentrated solutions, usually in 
crystalline masses consisting of minute six-sided plates. The 
mass, as seen in commercial "granulated grape sugar," looks 
very much like granulated sugar. It crystallizes from alcohol 
in monoclinic crystals. The sweetness of glucose is to that of 
cane sugar as 3 to 5. Its solutions turn the plane of polariza- 
tion to the right. 

Glucose is easily oxidized, reducing the salts of silver and 
copper. When treated with nascent hydrogen, it yields Sorbite 
(which see) . Under the influence of yeast it ferments, yielding 
mainly alcohol and carbon dioxide. Putrid cheese transforms 
it first into lactic acid and then into butyric acid by the so-called 
lactic acid fermentation. 



GLUCOSE. 181 

Glucose forms compounds with metals and salts. Among 
the better known compounds of this kind are those mentioned 
below : — 

Sodium glucose .... C 6 H n 6 . Na ; 

Sodium chloride glucose . 2 C 6 H la O G . NaCl + H 2 ; 

also C 6 H 12 6 . NaCl + £ H 2 0, and C 6 H 12 6 . 2 NaCl. These com- 
pounds, with sodium chloride, crystallize well, and can be easily 
obtained in pure condition. 

Cupric oxide glucose . . . C 6 H 12 6 .5 CuO. 

By treatment with acetic anhydride, glucose yields a product 
containing five acetyl groups, pent-acetyl-glucose, 

C 6 H 7 (C 2 H 3 0) 5 6 . 

Note for Student. — What does the formation of this compound 
indicate ? 

It is often important to know the quantity of 'glucose con- 
tained in a given liquid ; as, for example, in the urine in a case 
of suspected diabetes. For the purpose of making the estima- 
tion, advantage is taken of the action of glucose towards an 
alkaline solution of copper sulphate. The solution commonly 
used is that known as Fehling's solution. It is prepared by 
dissolving 34.64 g crystallized pure copper sulphate iu water, 
adding a solution of 200 g potassium sodium tartrate, and 600 g 
to 700 g caustic soda of the specific gravity 1.12, and diluting 
so that the whole makes one litre. 

Experiment 38. Make half the quantity of Fehling's solution 
above mentioned, and put in a bottle with a glass stopper. In a test- 
tube boil about 10 cc of this solution, and then add a few drops of a 
dilute solution of glucose. Continue to boil, and acid a little more of 
the glucose solution ; and so on, until, on removing the tube from the 
lamp, a dark-reel uniform-looking precipitate settles, leaving the liquid 
above it perfectly clear and colorless. This precipitate is cuprous 
oxide. By taking proper precautions, the exact amount of glucose 
present in a solution can be estimated in this way. 



182 CARBOHYDRATES. 

Ordinary glucose is known as d-glucose on account of its 
dextro-rotatory power. Both ^-glucose and i-glucose have been 
made. 

Fructose, fruit sugar (levulose), C 6 Hi 2 6 . — This sugar 
occurs together with glucose, and in equivalent quantities, in 
fruits ; and is formed by the action of dilute mineral acids, or 
ferments, on cane sugar. Pure fructose is obtained by heating 
inulin, a carbohydrate of the formula C^H^O^, with very dilute 
acids. It is also formed by the oxidation of d-mannite. 

Ordinary fructose is called d-fructose, although it turns the 
plane of polarization to the left. The reason for this is that it 
is related to other substances that are dextro-rotatory. 

Fructose can be obtained in the form of crystals. It is about 
as sweet as cane sugar, and has been proposed as a substitute 
for this in diabetes. 

i-Pructose has been made artificially in three ways : 1. By 
polymerisation of formic aldehyde, CH 2 0, under the influence 
of bases ; 2. By successive treatment of acrolein with bromine 
and baryta water; and 3. By the action of a weak alkali on 
the glycerose obtained by oxidation of glycerin. 

When i-fructose is treated with yeast, it is partly transformed 
b}* the ferment into alcohol and carbon dioxide. It is the 
d-fructose contained in it that undergoes the change, while the 
^-fructose remains behind unchanged, and can thus be obtained 
free from the other two varieties. 

Constitution of glucose and fructose. — Two reactions have 
been of special value in the determination of the constitution 
of the members of the group of monosaccharides. 

a. When either an aldehyde or an acetone is treated with 
hydrocyanic acid, an addition-product is formed thus : — 



H H 

I I 

CH 3 .C = + HCN = CH 3 .C< 



OH. 

CN ' 



and ch:> c = o+hcn =ch:> c <c5- 



FRUCTOSE. • 183 

The products can be converted into corresponding acids by 
the change of the cyanogen group into carboxyl. By the aid 
of these reactions it has been shown that glucose is an aldehyde, 
and fructose a ketone, of these formulas : — 

CH 2 OH 
CHO | 

I CO 

(CHOH) 4 | 

I (CHOH) 3 

CH 2 OH | 

CH 2 OH 

Glucose. Fructose. 

By adding hydrocyanic acid to glucose, transforming the 
nitrile into the acid, and reducing the acid, the product obtained 
was found to be a normal acid of the formula CH 3 . (CH 2 ) 5 .C0 2 H ; 
while the product obtained in the same way from fructose was 
found to have the formula 

CH 3 .CH< C ^ 2H 

(CH 2 ) 3 . CH 3 . 

These facts can only be explained on the assumption that 
glucose and fructose have the formulas above assigned to them. 

b. When an aldehyde or an acetone is treated with phenyl- 
hydrazine, C 6 H 5 . NH.NH 2 , a reaction takes place, as represented 
in this equation : — 

H H 

I I 

R.C = + H,N.NHC 6 H 5 = R.C = N.NHC 6 H 5 + H 2 0. 

The products thus formed are called hydrazones. 

The sugars form hydrazones, and if an excess of phenyl- 
hydrazine is used, a second reaction takes place involving the 
introduction of a second residue of phenylhydrazine. The 
products thus formed are called osazones. Thus from both 
glucose and fructose an osazone of the formula 

CH 2 OH(CHOH) 3 .C-C 

II II 
C 6 H 5 . HN . N N . NHC 6 H 5 , is obtained. 



184 CARBOHYDRATES. 

These osazones have made the thorough investigation of the 
sugars possible, as they are almost insoluble in water and have 
characteristic properties. By their aid sugars can be separated 
from their solutions, and can be recognized. The osazones 
can be converted into sugars. 

Mannose, C 6 Hi20 6 . — d-Mannose is one of the products of 
oxidation of cZ-mannite, and is obtained by the action of dilute 
acids on some kinds of cellulose. The shavings formed in the 
manufacture of buttons from vegetable ivory are rich in the 
cellulose which yields d-mannose. 

^-Mannose and i-mannose have also been prepared. 

The mannoses are aldehydes, and are stereoisomeric with 
glucose. 

Galactose, C 6 Hi20 6 d-Galactose is formed by treatment 

of sugar of milk with dilute acids, d-glucose being formed at 
the same time. Other carbohydrates also yield it. I- and 
^-galactoses are known. By reduction d- and ^-galactoses are 
transformed into dulcite. By oxydation all three galactoses 
yield mucic acid. 

2. Polysaccharides or Complex Sugars. 

Cane sugar, C12H22O11. — This well-known variety of sugar 
occurs very widely distributed in nature, in sugar cane, sorghum, 
the Java palm, the sugar maple, beets, madder root, coffee, 
walnuts, hazel nuts, sweet and bitter almonds ; in the blossoms 
of many plants ; in honey, etc., etc. 

It is obtained mainly from the sugar cane and from beets. 
In either case the processes of extraction and refining are largely 
mechanical. When sugar cane is used, this is macerated with 
water to dissolve the sugar. Thus a dark-colored solution is 
obtained. This is evaporated, and then passed through filters 
of bone-black which remove the coloring matter. The solu- 
tion is evaporated in the air to some extent, and then in 
large vessels called " vacuum pans," from which the air is 



CANE SUGAR. 185 

partly exhausted, so that the boiling takes place at a lower 
temperature than would be required under the ordinary pres- 
sure of the atmosphere. The mixture of crystals and mother 
liquors obtained from the "vacuum pans" is freed from the 
liquid by being brought into the " centrifugals." These are 
funnel-shaped sieves which are revolved very rapidly, the liquid 
being thus thrown by centrifugal force through the openings 
of the sieve, while the crystals remain behind and are thus 
nearly dried. The final drying is effected by placing the crys- 
tals in a warm room. 

"When beets are used the process is essentially the same, 
though there are some differences in the details. 

The mother liquors which are obtained from the "centrif- 
ugals " are further evaporated, and yield lower grades of sugar ; 
and, finally, a syrup is obtained which does not crystallize. 
This is molasses. Molasses is sometimes brought into the 
market as such ; sometimes, parti cularly when obtained from 
beet sugar, it is allowed to ferment for the purpose of making 
alcohol. The spent wash, or waste liquor, " vinasse," is now 
evaporated to dryness and calcined for the purpose of getting 
the alkaline salts contained in the residues. The products of 
distillation are collected, and from them tri-methyl-amine is 
separated (see p. 96). 

Sugar crystallizes from water in well-formed, large mono- 
clinic prisms. It is dextro-rotatory. When heated to 210° to 
220°, cane sugar loses water, and is converted into the substance 
called caramel, which is more or less brown in color, according 
to the duration of the heating and the temperature reached. 
Boiled with dilute acids, cane sugar is split into equal parts 
of glucose and fructose, as has been stated. The mixture of 
the two is called invert-sugar. The process is called inversion. 
It takes place, to some extent, when impure sugar is allowed 
to stand. Hence invert-sugar is contained in the brown sugars 
found in the market. Yeast gradually transforms cane sugar 
into glucose and fructose, and these then undergo fermentation. 
Cane sugar itself does not ferment. 



186 CARBOHYDRATES. 

Experiment 39. Arrange two pieces of apparatus as in Exp. 7. 
In one put 40s to 50s grape sugar and a certain quantity of yeast, as 
in Exp. 7; in the other put the same amount of cane sugar and of 
yeast. Notice the difference. 

Cane sugar does not reduce an alkaline solution of copper 
sulphate. 

Experiment 40. Prepare a dilute solution of cane sugar by dis- 
solving is to 2s in 200 cc water. Test this with Eehling's solution, 
as in Exp. 38. Now acid to the sugar solution 10 drops concentrated 
hydrochloric acid, and heat for half an hour on the water-bath at 
100°; exactly neutralize the acid with a dilute solution of sodium 
carbonate, and test with Eehling's solution. 

Oxidizing agents readily convert cane sugar into oxalic acid 
(see Exp. 34) and saccharic acid. 

Like glucose, cane sugar forms compounds with metals, 
metallic oxides, and salts. Among these the following may 
be mentioned : — 

Sodium sucr ate .... C 12 H 21 O u . Na, 

/Sodium-chloride s iterate . . C 12 H 22 O u . NaCl, 

Calcium sucrate .... C^H^On . Ca, 

and Lime sucrate C 12 H 22 O u . 2 CaO. 

These derivatives are not sweet. 

An oct-acetate of the formula C ]2 H 14 (C 2 H30) 8 O u has been 
made \>y treating sugar with sodium acetate and acetic anhy- 
dride. 

Though cane sugar readily breaks up into glucose and fruc- 
tose, no one has succeeded as yet in effecting the union of these 
two substances to form cane sugar. The character of the rela- 
tion between it and the two monosaccharides is not understood. 

Sugar of milk, lactose, Ci 2 H 22 O n + H 2 0. — This sugar 
occurs in the milk of all mammals, and is obtained in the manu- 
facture of cheese. The casein is separated from the milk by 






CELLULOSE. 187 

means of rennet; the sugar of milk remains in solution, is 
separated by evaporation, and purified b}* recrystallization. It 
crystallizes in rhombic crystals. That which comes into the 
market has been crystallized on strings or wood splinters. It 
has a slightly sweet taste ; is much less soluble in water than 
cane sugar, and is dextro-rotatory. It reduces Fehling's solu- 
tion. Oxidized with nitric acid, it yields mucic and saccharic 
acids. Nascent hydrogen converts sugar of milk into mannite, 
dulcite, and other substances. Like glucose and cane sugar, 
it forms compounds with bases, dissolving lime, baryta, lead 
oxide, etc. 

Sugar of milk ferments under certain circumstances, and 
is thus converted into lactic acid. The souring of milk is a 
result of this fermentation. The lactic acid formed coagulates 
the casein ; hence the thickening. 

Maltose, C^I^On. — This carbohydrate is formed by the 
action of malt on starch. Malt, which is made by steeping 
barley in water until it germinates, and then drying it, contains 
a substance called diastase, which has the power of effecting 
changes similar to some of those effected by the ferments. 
Thus, it acts upon starch, and converts it into dextrin and 
maltose : — 

3 C 6 H 10 O 5 -f- H 2 = C 12 H 22 O n -J- C 6 H 10 O 5 . 

Starch. Maltose. Dextrin. 

Maltose is also formed by the action of dilute sulphuric acid 
upon starch, and is hence contained in commercial glucoses. 
By further treatment with sulphuric acid it is converted into 
glucose. Maltose crystallizes in fine needles ; is dextro-rota- 
tory ; reduces Fehling's solution, and ferments with yeast. 

3. Polysaccharides, not Resembling Sugars. 

Cellulose, (C 6 Hio0 5 )*. — Cellulose forms the ground work 
of all vegetable tissues. It presents different appearances 
and different properties, according to the source from which it 



188 CARBOHYDRATES. 

is obtained ; but these differences are due to substances with 
which the cellulose is mixed ; and when they are removed, 
the cellulose left behind is the same thing, no matter what 
its source may have been. The coarse wood of trees, as well 
as the tender shoots of the most delicate plants, all contain 
cellulose as an essential constituent. It forms the membrane 
of the cells. Cotton-wool, hemp, and flax consist almost 
wholly of cellulose. 

For the preparation of cellulose, either Swedish filter-paper 
or cotton-wool may be taken. 

Experiment 41. Treat some cotton-wool successively with ether, 

alcohol, water, a caustic alkali, and, finally, a dilute acid. Then wash 

with water. 

i 

Cellulose is amorphous ; insoluble in all ordinary solvents ; 
soluble in an ammoniacal solution of cupric oxide. It dis- 
solves in concentrated sulphuric acid. If the solution is 
diluted and boiled, the cellulose is converted into dextrin 
and glucose. It will thus be seen that rags, paper, and 
wood, which consist largely of cellulose, might be used for 
the preparation of glucose, and consequently of alcohol. 

Experiment 42. Dissolve a sheet or two of filter-paper in as small 
a quantity of concentrated sulphuric acid as will suffice ; dilute with 
water to about half to three-quarters of a litre, and boil for an hour. 
Remove the sulphuric acid by means of chalk ; filter ; evaporate ; and 
test for glucose by means of Fehling's solution. 

Gun cotton, pyroxylin, nitro-cellulose. — Cellulose has 
some of the properties of alcohols ; among them the power to 
form ethereal salts with acids. Thus, when treated with nitric 
acid, it forms several nitrates, just as glycerin forms the nitrates 
known as nitro- glycerin (which see). 

Treated for a short time with sulphuric and nitric acids, 
cellulose is converted into the lower nitrates, particularly the 



STARCH. 189 

tetra- and penta-nitrates. A solution of these in a mixture of 
ether and alcohol is known as collodion solution, which is much 
used in photography. When poured upon any surface, such as 
glass, the ether and alcohol rapidly evaporate, leaving a thin 
coating of the nitrates which were in solution. 

When treated for twenty-four hours at 10° with a mixture 
of nitric and sulphuric acids, cellulose yields the hexa-nitrate 
C 12 H 14 4 (0. N0 2 ) 6 5 which is used as an explosive under the 
name of gun cotton. It is used chiefly for blasting. 

An intimate mixture of gun cotton and camphor has come 
into extensive use under the name of celluloid. As it is plastic 
at a slightly elevated temperature, it can easily be moulded into 
any desired shape. When it cools it hardens. 

Paper. — Paper in its many forms consists mainly of cellu- 
lose. The essential features in the manufacture of paper are, 
first, the disintegration of the substances used. This is effected 
partly mechanically, and partly bj* boiling with caustic soda. 
The mass is converted into pulp by means of knives placed on 
rollers. The pulp, with the necessary quantity of water, is 
then passed between rollers. Chiefly rags of cotton or linen 
are used in the manufacture of paper ; wood and straw are 
also used. 

Starch, (CeHioOs)*. — Starch is found everywhere in the vege- 
table kingdom in large quantity, particularly in all kinds of 
grain, as maize, wheat, etc. ; in tubers, as the potato, arrow- 
root, etc. ; in fruits, as chestnuts, acorns, etc. 

In the United States starch is manufactured mainly from 
maize ; in Europe, from potatoes. 

The processes involved in the manufacture of starch are 
mostly mechanical. The maize is first treated with warm 
water ; the softened grain is then ground between stones, a 
stream of water running continuously into the mill. The thin 
paste which is carried awa} T is brought upon sieves of silk bolt- 



190 CARBOHYDRATES. 

ing-cloth, which are kept in constant motion. The starch passes 
through with the water as a milk}' fluid, and this is allowed to 
settle when the water is drawn off. The starch is next treated 
with water containing a little alkali (caustic soda, or sodium 
carbonate), the object of which is to dissolve gluten, oil, etc. 
The mixture is now brought into shallow, long wooden runs, 
where the starch is deposited, the alkaline water running off. 
Finally, the starch is washed with water, and dried at a low 
temperature. 

Starch has a granular structure, the grains as seen under the 
microscope having a series of concentric markings, the nucleus 
of which is at one side. 

Starch in its usual condition is insoluble in water. If ground 
with cold water, it is partly dissolved. If heated with water, 
the membranes of the starch-cells are broken, and the contents 
form a partial solution. On cooling, it forms a transparent 
jelly called starch paste. 

With iodine, starch paste gives a deep blue color ; with bro- 
mine, a yellow color. 

Experiment 43. Make some starch paste thus : Put a few grams 
of starch 1 in an evaporating dish ; pour enough cold water upon it to 
cover it; grind it under the water with a pestle, and then pour 200 cc to 
300 cc hot water upon it. When this is cool, add a few drops to a litre 
of water, and then add a few drops of potassium iodide. As long as 
the iodine is in combination with the potassium no change of color 
takes place ; but if the iodine is set free by the addition of a drop or 
two of chlorine water, or of strong nitric acid, the entire liquid turns 
a beautiful dark blue. The cause of this color is the formation of a 
very unstable compound of starch and iodine. The color is easily 
destroyed by a slight excess of chlorine water (try it in a test-tube) ; 
by alkalies (try it) ; by sulphurous acid (try it) ; by hydrogen sulphide 
(try it) ; etc. It is also destroyed by heating. (Heat some of the 
solution in a test-tube, and let it stand.) The color reappears on 
cooling. 

1 The purest form of starch to be found in the market is that made from arrow-root 
Ordinary starch contains other substances which sometimes interfere with the reactions. 



GUMS. 191 

Experiment 44. Use some of the starch paste in studying the 
effect of bromine upon it. Use dilute solutions. The bromine must 
be in the free condition. 

It has been stated that starch is converted into dextrin, mal- 
tose, and glucose by dilute acids ; and that diastase converts 
it into maltose and dextrin. 

Experiment 45. Add 20 cc concentrated hydrochloric acid to 200 cc 
of the starch paste already made, and heat for two hours on the water- 
bath, connecting the flask with an inverted condenser (see Fig. 8). 
Then examine with Fehling's solution. Test, also, some of the original 
starch paste with Fehling's solution. 

Dextrin, C 6 H 10 O 5 . — Dextrin, as has been stated, is formed 
by treating starch with dilute acids or diastase. It is converted 
by further treatment with acids into glucose. The substance 
ordinarily called dextrin has been shown to be a mixture of 
several isomeric substances which resemble each other very 
closely. The mixture is an uncrystallizable solid. It is 
strongly dextro-rotatory ; gives a red color with iodine, and 
does not reduce Fehling's solution. It is used extensively as 
a substitute for gum. 

Gums. — Under this head are included a number of sub- 
stances which occur in nature. One of the best known is gum 
arable, which is obtained in Senegambia from the bark of trees 
belonging to the Acacia variety. Its formula, like that of cane 
sugar, is C^E^On- Other gums are wood gum, obtained from 
the birch, ash, beech, etc. ; bassorin, the chief constituent of 
gum tragacanth, etc. 

Our knowledge of the chemistry of these gums is very limited. 



CHAPTER XIL 
MIXED COMPOUNDS CONTAINING NITROGEN. 

In speaking of the preparation of dibasic acids from mono- 
basic acids, reference was made to cyan-acetic and the two 
cyan-propionic acids. These are nothing but simple cyanogen 
substitution-products analogous to chlor-acetic and the two 
chlor-propionic acids. They are made by treating the chlorine 
products with potassium cyanide. They have been useful 
chiefly in the preparation of dibasic acids, as described in con- 
nection with malonic and the two succinic acids. It will there- 
fore not be necessary to consider them individually here. 

Note for Student. — How can malonic be made from acetic acid; 
and the two succinic acids from propionic acid ? Give the equations. 

The chief substances to be considered under the head of 
mixed compounds containing nitrogen are the amido-acids and 
the acid amides. As will be seen, both these classes of sub- 
stances are of special interest, as they represent forms of com- 
bination which are favorite ones in nature, especially in the 
animal kingdom, some of the most important substances found 
in the animal body, such as urea, uric acid, glycocoll, etc., 
belonging to one or both the classes. 

Amido-acids. 

The relation of an amido-acid to the simple acid is, as the 
name implies, the same as that of an amido derivative of a 
hydrocarbon to the hydrocarbon. That is to say, it may be 
regarded as the acid in which a hydrogen is replaced by the 
amido group, NH 2 . Thus, amido-acetic acid is represented 



AMIDOFORMIC ACID. 193 

■NTTT 

by the formula CH 2 < 2 ' ; while amiclo-methane, or methyl- 
C0 2 H 

amine is represented thus, CH 3 .NH 2 . The reasons for regard- 
ing methyl-amine as a substituted ammonia, as represented, 
have been stated. The formula is based upon the reactions 
of the substance ; that is, upon its chemical conduct and the 
methods used in its preparation. The same arguments lead 
in the same way to the view that the amido-acids are 
substituted ammonias, and, at the same time, acids. The 
simplest method for their preparation consists in treating 
halogen derivatives of the acids with ammonia ; thus amido- 
acetic acid can be made by treating brom-acetic acid with 
ammonia : — 

CH2 <co 2 h + 2NH3 = ch -'<cSh + nh ^ 

Note for Student. — Compare this reaction with that made use 
of for making methyl-amine. 

NH 2 
Amido-formic acid, carbamic acid, I . — This acid 

0O 2 H 

is not known iu the free condition. Its ammonium salt, 
NH 2 

I , is formed when carbon dioxide and ammonia are 

C0 2 NH 4 

brought together : — 

NH 9 
I 
C0 2 + 2 NH 3 = C0 2 NH 4 . 

The other carbamates are prepared from the ammonium 
salt. They are decomposed, yielding carbonates and ammonia. 
Thus, when potassium carbamate is warmed in water solution, 
decomposition takes place, as represented in the equation, — 

NH 2 .C0 2 K + H 2 = NH 3 + HKC0 3 . 

The ethereal salts of carbamic acid are readily made by 



194 MIXED COMPOUNDS CONTAINING NITROGEN. 

treating the ethereal salts of chlor-formic acid (see p. 157) 
with ammonia : — 

CI NH 2 

I I 

C0 2 C 2 H 5 + 2 NH 3 = C0 2 C 2 H 5 + NH 4 CL 

Amido-formic acid cannot be taken as a fair representative 
of the amido-acids, any more than carbonic acid can be taken 
as a fair representative of the hydroxy-acids. 

Glycocoll glycine, > Q Q / NH \ _ In the 

amido-acetic acid, ) V 00 2 H/ 

bile are contained two complicated acids, which are known as 
glycocholic and taurocholic acids. When glycocholic acid is 
boiled with hydrochloric acid, it breaks up, yielding cholic acid 
and glycocoll. In the urine of horses is found an acid known 
as hippuric acid. When this is boiled with hydrochloric acid, 
it breaks up into benzoic acid and glycocoll. 

When uric acid is treated with hydriodic acid, glycocoll is 
one of the products. Further, glycocoll is formed when glue 
is boiled with baryta water or dilute sulphuric acid. Its forma- 
tion from brom-acetic acid and ammonia, mentioned above, gives 
the clearest indication in regard to its relation to acetic acid. 

Amido-acetic acid has both acid and basic properties. It 
unites with acids, forming weak salts ; and it acts upon bases, 
giving salts with metals, — the amido-acetates. It also unites 
with salts, forming double compounds. 

Examples of the compounds with acids are the 

Hydrochloride .... CH 2 < *" , 

(_/0 2 H 

i + i, xr* * nxj ^NH 2 .HN0 3 

and the Nitrate CH 2 < 2 3 ; 

C0 2 H 

of the salts with metals, 

Zinc amido-acetate . Zn(C 2 H 4 N0 2 ) 2 4- H 2 0, 

and Copper amido-acetate . Cu(C 2 H 4 N0 2 ) 2 + H 2 ; 



AMIDO-PBOPIONIC ACIDS. 195 

of the compounds with salts, the double salt of 

Copper nitrate ) Cu ( N o 3 ) 2 .Cu(C 2 H 4 N0 2 ) 2 + 2 EUO. 

and Copper amido-acetate, ) 

Treated with nitrous acid, glycocoll is converted into hydroxy - 
acetic acid. 

Note fok Student. — Write the equation representing the reaction 
which takes place when glycocoll is treated with nitrous acid. 

Sarcosine, methyl-glycocoll, C 3 H 7 N0 2 (= CH 2 < ~ j, ; 

If brom-acetic acid is treated with methyl-amine instead of 
with ammonia, a reaction takes place similar to that which takes 
place with ammonia, the product being methyl glycocoll or sarco- 
sine : — 

CH * < ™ XT + 2 NH 3 «= CH * < m\j + NH * Br ; and 

CU 2 -H iA* 2 ri 

CH2 < CO H + 2 CH =- NH * = CH * < CO,H H3 + NH 3( CH ') Br - 

Sarcosine. 

Sarcosine is a product of the decomposition of creatine, which 
is found in flesh, and of caffeine, which is a constituent of coffee 
and tea. It is obtained from creatine and caffeine by boiling 
them with baryta water. 

Its properties are much like those of glycocoll. 

Amido-propionic acids, C.,H 7 NO,. — These acids bear to 
propionic acid relations similar to that which amido-acetic acid 
bears to acetic acid. There are two, corresponding to a- and 
/J-chlor-propionic acids, from which they are made. They are 
not found in nature. Their properties are much like those of 
glycocoll. 

Note for Student. — What substances would be formed by treat- 
ing the two amido-propionic acids with nitrous acids? 

Among the amido derivatives of the higher members of the 



196 MIXED COMPOUNDS CONTAINING NITROGEN. 

fatty acid series, that of caproic acid should be specially men- 
tioned. 

Leucine, a-amido-caproic acid, 

C 6 H 13 N0 2 [=CH 3 . CH 2 . CH 2 . CH 2 . OH(NH 2 ) . C0 2 H ] . 
Leucine is found very widely distributed in the animal kingdom, 
as in the spleen, pancreas, and brain. It has also been found 
in the vegetable kingdom in a few plants. It is produced by 
the decomposition of substances containing albumin or gelatin. 
It has been made by treating a-brom-caproic acid with ammonia. 

Amtdo-sulphonic Acids. 
Just as there are amido derivatives of the carbonic acids, 
so, too, there are amido derivatives of the sulphonic acids. 
Only one of these need be considered. 

TaUrine ' 1 P rr Tsrqo f- C TT <T S °3 H 

Amido-isethionic acid, I WtNBO,^- C A < ^ 

Taurine is found in combination with cholic acid in taurocholic 
acid, in ox bile and the bile of many animals, as well as in 

other animal liquids. It has been made synthetically from 

OH 
isethionic acid, C 2 H 4 < , by treating the acid successively 

0O3H. 

with phosphorus pentachloride and ammonia : — 
CA< S? 2 0H + 2PC1 > = CA <S0 2 C1 + 2P0C1 * + 2HC1; 

Isethionic acid. Chlor-ethyl-sulpbon-chloride. 

CA <S0 2 C1 +H2 ° = CA< S0 2 OH + HCI; 

Chlor-ethyl-sulphonic acid. 

CA< S0 2 OH + 2NH3 = CA <S + NH * CL 

Taurine. 

Taurine crystallizes in large tetragonal prisms. It is a very 
stable substance, and can be boiled with concentrated acids with- 
out decomposition. With nitrous acids it yields isethionic acid. 

It unites with bases forming salts. 



ACID AMIDES. 197 

The only amido- dibasic acid which need be considered is 
arnido-succinic acid. 

Aspartic acid, } Ci H ; No/= C^CNH.X ^H 

Amido-succmic acid, J V C0 2 H 

Aspartic acid occurs in pumpkin seeds, and is frequently 
met with as a product of boiling various natural compounds 
with dilute acids. Thus, for example, it is formed when casein 
and albumin are treated in this wa}\ It is formed also when 
asparagine (which see) is boiled with acids or alkalies. 

Aspartic acid ciTstallizes. It turns the plane of polarization, 
under some circumstances to the right, under others to the left. 

Treated with nitrous acids it yields malic acid. 

Acid Amides. 

When the ammonium salt of acetic acid is heated, it gives off 
water, and a body distils over which is known as acetamide. 
The reaction which takes place is represented by the following- 
equation : — 

CH 3 .COO]S T H 4 = CH3.CONEU + H 2 0. 

The substance obtained has neither acid nor basic properties. 
An examination of the ammonium salts of other acids shows 
that the reaction is a general one, and a class of neutral bodies, 
known as the acid amides, can thus be obtained. 

As no one of the acid amides of the fattj- acid series is of 
special importance, a few words of a general character in regard 
to the class will suffice. 

Besides the reaction above referred to for making the acid 
amides, there are two others of general application. One con- 
sists in treating an ethereal salt of an acid with ammonia ; 
thus, when ethyl acetate is treated with ammonia, this reaction 
takes place : — 

CH 3 .C0 2 C 2 H 5 + NH 3 = CHo.CONH, + C 2 H 6 0. 



198 MIXED COMPOUNDS CONTAINING NITROGEN. 

The other reaction consists in treating the acid chlorides with 
ammonia. Thus, to get acetamide, we may treat acetyl chloride 
(see p. 61) with ammonia: — 

CH3.COCI + 2NH 3 = CH 3 .CONH 2 -f NH 4 C1. 

This last reaction is perhaps used most frequently. It shows 
the relation which exists between acetic acid and acetamide. 
For acet}'l chloride is made from acetic acid by treatment with 
phosphorus trichloride, and is, therefore, as has been pointed 
out, to be regarded as acetic acid in which the hydroxy 1 is 
replaced by chlorine. Now, by treatment with ammonia the 
same reaction takes place as that which we have had to deal 
with in the preparation of amido-acids, the chlorine is replaced 
by the amido group. Therefore, acetamide is acetic acid in 
which the hydroxyl is replaced by the amido group, as shown 
in the formulas : — 

O O 

I I 

CH3.C-OH CH 3 -C-NH 2 . 

Acetic acid. Acetamide. 

As the acid hydrogen of the acid is replaced, the amide is not 
an acid. On the other hand, the basic properties of the am- 
monia are destroyed by the presence of the acid residue as a 
part of its composition. This latter fact may be stated in 
another way ; viz., when an ammonia residue is in combination 
with carbon, which in turn is in combination with oxygen, its 
basic properties are destroyed. 

The amides are converted into ammonia and a salt when 
boiled with strong bases : — 

CH3.CONH, -f KOH = CH 3 C0 2 K + NH 3 . 

They are converted into cyanides by treatment with phos- 
phorus pentoxide P 2 5 : — 

CH 3 .CONH 2 = CH 3 .CN + H 2 0. 

As the substance obtained in this way is identical with methyl 






ACID AMIDES. 



199 



Dyanide, which is formed by treating methyl-sulphuric acid with 
potassium cyanide, the reaction furnishes additional evidence 
in favor of the conclusion already reached; viz., that in the 
cyanides the carbon and not the nitrogen of the cyanogen 
group is in combination with the hydrocarbon residue, as repre- 
sented in the formula CH 3 — C — N. 

As acetamide is made b\' treating ammonia with the chloride 
of acetic acid, so, by treating ammonia with the chloride of any 
acid, the corresponding amide can be made. So', also, by treat- 
ing ammonia with acid chlorides, or by treating acid amides with 
strong acids, more complicated compounds can be obtained. 

fCHO f C * H 3° 

Of these di-acetamide, NHj 2 :i , and tri-acetamide, N-j C 2 H 3 ? 

CCA ° lc 2 H 3 

may serve as examples. The relations of these substances to 
ammonia and to acetic acid are shown by the formulas, ordinary 
or mon-acetamide being NH 2 .C 2 H 3 or CH 3 .CO.NH 2 » 




Fig. 12. 

Experiment 46. Arrange an apparatus as shown in Fig. 12. In 

flask A put 50s oxalic acid (dehydrated at 100°) and 50s absolute alco- 
hol; and, in flask B, 50s absolute alcohol. Heat the bath D to 10CP; 
and then heat the alcohol in flask B to boiling, and continue to pass 



200 MIXED COMPOUNDS CONTAINING NITROGEN. 

the vapor from flask B into the mixture in flask A, meanwhile allowing 
the temperature of the oil-bath to rise to 125°-130°. A mixture of 
alcohol and ethyl oxalate will distil over, while the ethyl oxalate will 
be mostly in flask A. Add concentrated ammonia to some of the ethyl 
oxalate. Oxamide is thrown down as a white powder. What reactions 
have taken place? Write the equations. Filter ®ff the oxamide, and 
wash it with water. See whether it conducts itself like an acid. Has 
it an acid reaction? Boil with caustic potash (not too much), and 
notice whether ammonia is given off. Why does-it dissolve? How can 
the oxalic acid be extracted from the solution? 

When the amide of a poly-basic acid is boiled with amirib- 
nia, and under some other circumstances, partial decomposition 
takes place, and a substance is formed which is both amide and 

acid. Thus, in the case of oxamide, the product is oxamic 

C0 2 H 
acid, I . This acid forms well-characterized salts and 

CONH, 

other derivatives such as are obtained from acids in general. 
There is one acid of this kind which is a well-known natural 
substance. It has already been referred to in connection with 
aspartic acid, which is closely related to it. It is 

Asparagine, amido-snocinamic acid, 

C 4 H 8 N 2 3 + H 2 c/= C 2 H 3 (NH 2 ) < ^^ H2 V— Asparagine is 

found in many plants, as in asparagus, liquorice, beets, peas, 
beans, vetches, etc. It can be made by treating mon-ethyl- 
amido-succinate with ammonia. 

Note for Student. — What reaction takes place ? Write the 
equation. 

Asparagine forms large rhombic crystals, difficultly soluble 
in cold water, more easily in hot water. When boiled with 
acids or alkalies, it is converted into aspartic acid and ammonia. 

Note for Student. — Notice that only the amido group of the 
amide is driven out of the compound by this treatment. The other 
amido group which is contained in the hydrocarbon portion of the 
compound is not disturbed. 

Nitrous acid converts asparagine into malic acid. 



CREATINE. 201 

Cyan-amides, CN 2 H 2 . — In speaking of cyanic acid, the 
.existence of two chlorides of cyanogen was mentioned : one 
a liquid, having the formula CNC1 ; the other a solid, of the 
formula C 3 N 3 C1 3 . When the former is treated with ammonia, 
it is converted into an amide, CN.NH 2 , which bears to cyanic 
acid, CN.OH, the relation of an amide. Like the other 
simple compounds of cyanogen, cyan-amide readily undergoes 
change. When simply kept unmolested, it is converted into 
di-cyan-diamide, C 2 N 4 H 4 ; while, when heated to 150°, a violent 
reaction takes place, and tri-cyan-triamide, C 3 N 6 H 6 , is formed. 
The latter compound is also called, melamine and cyanuramide, 
and from certain methods of formation it is concluded that it 
is the amide of cyanuric acid. It is a powerful mon-acid 
base. The formation of these compounds is particularly 
interesting, as illustrating the tendency on the part of the 
simpler cyanides to undergo change under slight provo- 
cation. 

Guanidine, CN 3 H 5 . — This substance, which is closely related 
to cyan-amide, is formed by the oxidation of guanine (which 
see) , and this in turn is obtained from guano. It can also be 
made by treating cyanogen iodide with ammonia : — 

CNI + 2M 3 = CN 3 H 5 .HI, 
the product being the hydriodic acid salt of guanidine. As 
will be seen, guanidine is cyan-amide plus ammonia : — 
CN . NH 2 + NH 3 = CN 3 H 5 . 

It is a strongly alkaline base. Boiled, with dilute sulphuric 
acid or baryta water, it yields urea and ammonia : — ■ 

CN 3 H 5 + H 2 = CON 2 H 4 + NH 3 . 

Guanidine. Urea. 

Creatine, C 4 H 9 N 3 2 . — This substance is found in the 
muscles of all animals. It is closely related to guanidine and 



202 MIXED COMPOUNDS CONTAINING NITROGEN. 

also to sarcosine (see p. 195). It has been made synthetically 
by bringing eyan-amide and sarcosine together. The reaction 
which takes place is analogous to that made use of for the 
preparation of guanidine. The analogy is shown by the two 
equations, — 

CN.NH 2 + NH 8 = CN 3 H 5 , 

Gruanidine. 

or (CN 2 H 3 .NH 2 ), 
and CN . NH 2 + N -] CH 3 = CN 2 H 3 . N | CH3 

L CH 2 .COoH Creatine. I CH 2 .C0 2 H, 



L 2 • KJ V/ 2 J 

Sarcosine. 



or C 4 H 9 N 3 2 . 



Urea, or carbamide and derivatives. — Closely related 
to the nitrogen compounds just considered is urea, or the 
amide of carbonic acid. Its importance and certain peculiari- 
ties distinguish it from the other acid amides, and it is there- 
fore considered by itself. 

Urea is found in the urine and blood of all mammals, and 
particularly in the urine of carnivorous animals. Human 
urine contains from 2 to 3 per cent ; the quantity given off by 
an adult man in 24 hours being about 30 s . Urea can be made 
by the following methods : — 

(1) By treating carbonyl chloride with ammonia : — 

COCl 2 + 2 NH 3 = CON 2 H 4 + 2 HC1. 
What is the analogous reaction for the preparation of acetamide? 

(2) By heating ammonium carbamate : — 

CO<^2 =CON 2 H 4 + H 2 0. 
DIN ±±4 

What is the analogous reaction for preparing oxamide? 

(3) By treating ethyl carbonate with ammonia : — 

CO < °^ 5 + 2 NH 3 = CON 2 H 4 + 2 C^O, 
OC 2 H 5 



UREA. 203 

(4) By the addition of water to cyan-amide : — 

CN.NH 2 + H 2 = CON 2 H 4 . 

(5) By evaporation of ammonium cyanate in aqueous solu- 
tion : — 

CN(ONBU = CON 2 H 4 . 

This reaction is of special interest, for the reason that it 
afforded the first example of the formation, by artificial methods 
from inorganic substances, of an organic compound found in 
the animal body (see p. 1). 

Urea is most readily obtained from urine. 

Experiment 47. Evaporate four or five litres fresh urine to a thin, 
syrupy consistence. After cooling add ordinary concentrated nitric 
acid, when crystals of urea nitrate are obtained. Filter, wash, and 
recrystallize from moderately concentrated nitric acid. When the 
crystals of urea nitrate are white, dissolve again in water, and add 
finely-powdered barium carbonate. The nitric acid forms barium 
nitrate, and the urea is left in free condition. Evaporate to dryness, 
and from the residue extract the urea with strong alcohol. 

Experiment 48. Make potassium cyanate as directed in Experi- 
ments 24, p. 82, and 26, p. 83. Extract the cyanate with cold water, and 
add a solution of ammonium sulphate containing as much of the salt as 
there was used of potassium ferrocyanide in the preparation of the 
cyanate. Evaporate to a small volume, and allow to cool. Potassium 
sulphate will crystallize out. Filter this off, and evaporate to dryness. 
Extract with alcohol. The urea will crystallize from the alcoholic 
solution when it is brought to the proper concentration. Give all the 
reactions involved in passing from potassium ferrocyanide to urea. 
Compare the urea made artificially with that made from urine. 

Urea crystallizes from alcohol in large quadratic prisms, 
which melt at 132°. 

Experiment 49. Determine the melting-points of both the natural 
and artificial specimens of urea. 

Urea is easily soluble in water and alcohol. Heated with water 



204 MIXED COMPOUNDS CONTAINING NITROGEN. 

in a sealed tube to 100°, it breaks up into carbon dioxide 
and ammonia : — 

CON 2 H 4 + H 2 = C0 2 + 2 NH 3 . 

The same decomposition of the urea takes place spontaneously 
when urine is allowed to stand. Hence the odor of ammonia 
is always noticed in the neighborhood of urinals which are not 
kept thoroughly clean. 

Sodium hypochlorite or hypobromite decomposes urea into 
carbon dioxide, nitrogen, and water : — 

CON 2 H 4 + 3 NaOCl = Na 2 C0 3 + NaCl + N 2 + H 2 + 2 HC1. 

Experiment 50. To a solution of 20^ sodium hydroxide in 100 cc 
water add about 5 CC bromine, and shake well. Make a solution of urea 
in water, and add to the solution of the hypobromite. An evolution 
of gas will be noticed, showing that the urea is decomposed. 

Nitrous acid acts in the same way : — 

CON 2 H 4 + 2 HN0 2 = C0 2 + N 4 + 3 H 2 0. 

When heated, urea loses ammonia, and yields first biuret, 
and finally cyanuric acid (see p. 84) : — ■ 

2CO(NH 2 ) 2 = C 2 H 5 N 3 2 + NH 3 ; 

Biuret. 

3 CO(NH 2 ) 2 = C 3 H 3 3 N 3 + 3 NH 3 . 

Cyanuric acid. 

Urea unites with acids, bases, and salts. The hydrogen of 
the amido groups can be replaced by acid or alcohol radicals, 

NIT C "FT O 

giving compounds of which acetyl urea, CO < 2 3 , and 

NHC H -^"-^ 

ethyl urea, CO < ^ TtT 2 5 , are examples. 

2 
Among the compounds with acids, the following may be 

mentioned : urea hydrochloride, CH 4 N 2 . HC1 ; urea nitrate, 

CH 4 N 2 O.HN0 3 ; and urea phosphate, CH 4 N 2 . H 3 P0 4 . With 

metals it forms such compounds as that with mercuric oxide, 

HgO.CH 4 N 2 ; with silver, CH 2 N 2 0. Ag 2 , etc. With salts it forms 

such compounds as HgCl 2 . CH 4 N 2 0, HgO.CH 4 N 2 O.HN0 3 , etc. 



PARABANIC ACTD. 205 

Substituted ureas, — that is, those derivatives of urea which 
contain hydrocarbon residues in place of one or all the hydrogen 
atoms, — can be made from the cyanates of substituted ammo- 
nias. The fundamental reaction is the spontaneous transforma- 
tion of ammonium cyanate into urea : — 

CN.ONH 4 = CO(NH 2 ) 2 . 

In the same way, cyanates of substituted ammonias are trans- 
formed into substituted ureas : — 

CN .ONH 3 .C 2 H 5 = CO < ™ CsH5 ; - 

JN XI2 

CN.ONH 2 (C 2 H 5 ) 2 = CO < ^( C 2 H s)2 ? etc. 

NH 2 

The urea derivatives which contain acid radicals are made by 
treating urea with the acid chlorides : — 

C0< NH! + C 2 H 3 0C1 = CO <^ C2H3 °+ HC1. 

Acetyl urea. 

Note foii Student. — In what sense is acetyl urea analogous to 
acetamide? 

There are several derivatives of urea and radicals of dibasic 
acids, as oxalic and malonic acids, which are of special interest, 
as the}^ are closely related to uric acid ; and their formation from 
this acid has thrown much needed light upon the inner nature of 
the acid. 



Parabanic acid, 1 „ TT ^ T _ / CO.NH 

_ . . M- :5 H.,N.,O 3 = I >CO •— Parabanic 

Oxalylurea, J " V CO.NH / 

acid is formed by boiling uric acid with strong nitric acid and 

other oxidizing agents, and by treating a mixture of urea and 

oxalic acid with phosphorus trichloride : — 

C 2 H 2 4 + CO(NH 3 ) 2 = C S H 2 N 2 3 + 2 H 2 0. 



206 MIXED COMPOUNDS CONTAINING NITROGEN. 

It acts like an acid. Its salts readily pass over into salts of 
oxaluric acid (which see) . Treated with alkalies it breaks up 
into urea and oxalic acid. As will be seen, parabanic acid is 

CO NH 2 
analogous to oxamide, | , the residue of urea acting the 

CO . NH 2 
part of the two amido groups. 

/ CO.QH \ 

Oxaluric acid, C 3 H ± N 2 OA= CO.HN.CO.NhJ, bears to 
parabanic acid the same relation that oxamic acid bears to 
oxamide. It occurs in the form of the ammonium salt in small 
quantity in human urine. 



Barbituric acid, malonyl urea, 

C 4 H 4 N 2 3 + 2 HX>f = CH 2 < 22'S? > CO V — Barbituric 
\ CO.-Nxi / 

acid, like parabanic acid, is a product obtained from uric acid. 

It has been made artificially by treating a mixture of malonic 

acid and urea with phosphorus oxichloride : — 

CH 2 < COOH + CQ < NH : = CH2 < CO. NH > CQ + 2 ^ 

Treated with an alkali, barbituric acid breaks up into malonic 
acid and urea. 

The relation of the acid to malonic acid and urea is the same 
as that of parabanic acid to oxalic acid and urea. 



Sulpho-urea, CS(NH 2 ) 2 . — This substance is formed by 
heating ammonium sulpho-cyanate, the reaction which takes 
place being analogous to that by which urea is formed from 
ammonium cyanate : — 

CNSNH 4 = CS(NH 2 ) 2 . 

A number of derivatives of sulpho-urea have been made. 
They resemble those obtained from urea. 






XANTHINE. 207 

Uric acid, C 5 H 4 N 4 3 . — Uric acid occurs in human urine, 
in certain urinary calculi, in the urine of carnivorous animals, 
and of birds. The excrement of serpents consists almost 
entirely of ammonium urate. It has been made by heating 
together amido-acetic acid and urea, and by other methods. 

Uric acid is best prepared either from serpents' excrement or 
guano. 

It forms a crystalline powder, which is almost insoluble in 
water. It is a monobasic acid, though weak compounds with the 
alkali metals can be made which contain two atoms of metal 
in the molecule. 

Uric acid has been the subject of a large number of inter- 
esting investigations, and many derivatives have been obtained 
from it. It would only tend to confusion to give an account of 
man}' of these derivatives here. Hence only a few of the trans- 
formations which have been effected, and which give an insight 
into the nature of the acid, will be mentioned. 

1. By heating uric acid, ammonia, hydrocyanic acid and urea 
are formed. 

2. Heated with hydriodic acid, it yields carbon dioxide, ammo- 
nia, and glycine : — 

C 5 H 4 N 4 3 + 5 H 2 = 3 C0 2 + 3 NH 3 + C 2 H 5 N0 2 . 

3. Oxidizing agents convert uric acid either into allanto'in, 
a complicated substance of the formula C 4 H 6 N 4 3 , or alloxan, 
C 4 H 2 N 2 4 , which is closely related to parabanic acid, or oxalyl 
urea (see p. 205), and barbituric acid, or malonyl urea (see 
p. 206). 

Xanthine, C5H4N4O2, is found in some rare urinary calculi 
and in several animal liquids. It is formed by the action of 
nitrous acid on guanine, C 5 H 5 N 5 : — 

C 5 H 5 N 5 + HN0 2 - C 5 H 4 N 4 2 + H 2 + N 2 . 

It has been shown that this transformation involves 



208 MIXED COMPOUNDS CONTAINING NITROGEN. 

the replacement of an imide group, NH, by an atom of 
oxygen. 

substance found in chocolate prepared from the seed of the 
cacao tree. It has been made by treating the lead compound 
of xanthine with methyl iodide. 

Caffeine, theine, trimethyl-xanthine, 

C 8 H 10 N 4 O 2 + H 2 O[=C 5 H(CH 3 ) 3 N 4 O 2 + H 2 O], is the active 
constituent of coffee and tea. It has been made from theo- 
bromine by the introduction of a third methyl group. 

Thus, as will be seen, a close connection is established 
between the active constituents of coffee, tea, and chocolate on 
the one hand, and xanthine and guanine on the other. 

Guanine, C 5 H 5 N 5 0[=C5H 3 (NH 2 )N 4 0] i is found principally 
in guano, from which it is prepared. Nitrous acid converts it 
into xanthine. Oxidizing agents convert it into guanidine, 
CN 3 H 5 (seep. 199). 

Retrospect. 

Before passing on to the next division of our subject, it will 
be well to pause and consider briefly what we have learned 
thus far. 

In the first place, all the compounds which we have considered 
may be regarded as derived from the marsh-gas hydrocarbons 
or paraffins. 

By replacing the hydrogen atoms of these hydrocarbons with 
chlorine, bromine, or iodine, we get (1) the substitution-products 
of the hydrocarbons. 

By introducing hydroxyl into a hydrocarbon in place of 
hydrogen, we get the bodies called (2) alcohols, of which 



RETROSPECT. 209 

there are three classes : (a) the primary, (b) the secondary , 
and (c) the tertiary alcohols. 

By oxidizing primary alcohols we get (3) aldehydes. 

By oxidizing secondary alcohols we get (4) ketones. 

By oxidizing alcohols, aldehydes, and ketones, we get (5) 
acids. 

Acids and alcohols act upon each other, forming (6) ethereal 
salts, and alcohols can be converted into (7) ethers. 

Corresponding to the oxygen derivatives, we met with com- 
pounds containing sulphur, as (8) the sulphur alcohols, or 
mercaptans; (9) the sulphur ethers; and (10) the sulphonic 
acids. 

Next, we found compounds containing nitrogen. Under this 
head we considered cyanogen, and the allied compounds hydro- 
cyanic, cyanic, and sidpho-cyanic acids. Allied to these we 
found (11) the cyanides, and (12) the isocyanides ; (13) the 
cyanates, and (14) the isocyanates ; (15) the sulpho-cyanates, 
and (16) the iso-sulpho-cyanates or mustard oils. 

Finally, we found (17) compounds containing metals in combi- 
nation ivith radicals. 

Representatives of these various classes of compounds were 
studied, and the relations between them pointed out. 

We found poly-acid alcohols and poly-basic acids. 

Under the head of mixed compounds were found compounds 
which belong at the same time to two or more of the funda- 
mental classes, as the hydroxy -acids, the carbo-hydrates, and 
the amido-acids. A consideration of the amido-acids and 
the acid amides brought us naturally to the consideration of 
urea and its derivatives, and of uric acid and its derivatives. 

We turn now to a new class of compounds, known as unsatu- 
rated compounds. 



CHAPTER XIII. 

UNSATURATED CARBON COMPOUNDS. - DIS- 
TINCTION BETWEEN SATURATED AND 
UNSATURATED COMPOUNDS. 

All the compounds thus far studied are generally called 
saturated compounds. This is certainly an appropriate name 
as far as the hydrocarbons themselves and some of the classes 
of their derivatives are concerned. The expression ' ' saturated " 
is intended to signify that the compounds have no power to unite 
directly with other compounds or elements. Thus marsh gas 
cannot be made to unite directly with anything. Bromine, for 
example, must first displace hydrogen before it can enter into 
combination with the compound 

CH 4 + Br 2 = CH 3 Br + HBr. 

The compound is saturated. 

On the other hand, a compound which can take up elements 
or other compounds directly is called unsaturated. Thus, phos- 
phorus trichloride is unsaturated, for it has the power to take 
up two chlorine atoms thus : — 

PC1 3 + Cl 2 = PC1 5 . 

Ammonia is unsaturated, for it can take up other elements : — 

NH 3 + HC1 = NH.C1. 



UNSATURATED CARBON COMPOUNDS. 211 

The condition of unsaturation is met with among carbon 
compounds in several forms : — 

First. The aldehydes act like unsaturated compounds, as 
shown in their power to take up ammonia, hydrocyanic acid, 
and other substances. 

Second. The ketones also act like unsaturated compounds, 
though their power in this way is less marked than that of the 
aldehydes. 

Third. The substituted ammonias are unsaturated, in the 
same sense in which ammonia itself is unsaturated. 

Fourth. The cyanides take up hydrogen directly, and are 
therefore unsaturated also. 

In the substituted ammonias, and probably in the cyanides, 
the unsaturation is due to the same cause as that in ammonia. 
In them the nitrogen is trivalent. In contact with certain 
substances it becomes quinquivalent, and saturates itself. 

In the aldehydes and ketones, carbon is in combination with 
oxygen in the carbonyl condition. When they unite with 
hydrogen and some compounds, such as hydrocyanic acid, the 
relation between the carbon and oxygen is probably changed, 
the latter being in the hydroxyl condition. The changes are 
usually represented by formulas such as the following : — 



[3 • C \ XT + H 2 = 


cH,<sr 


CH 3 


CH 3 


1 
C = + HCN = 

1 


' /CN 
1 --OH' 



CH 3 CH 3 

In the carbonyl group the oxygen is represented as held by 
two bonds by the carbon atom, while in the hydroxyl condition 
it is represented as held by one bond. The signs may be used 
if care is taken to avoid a too literal interpretation of them. 
There are undoubtedly two relations which carbon and oxygen 



212 UNSATURATED CARBON COMPOUNDS. 

bear to each other in carbon compounds. These relations may 
be called the liydroxyl relation, represented by the sign C— O — , 
and the carbonyl relation, represented by the sign C = O. 

Fifth. There is a fifth kind of unsaturation, dependent upon 
differences in the relations between carbon atoms, and it is this 
kind which is ordinarily meant when unsaturated carbon com- 
pounds are spoken of. 

The kind of relation between the carbon atoms in all the 
saturated hydrocarbons is, so far as we know, the same as that 
which exists between the two carbon atoms of ethane, and 

H H 

I I 
which is represented by the formula H — C— C — H. This 

I I 

H H 

formula signifies simply that the two carbon atoms are held 
together hy the forces which in marsh gas enabled each carbon 
atom to hold one hydrogen atom. Abstracting one hydrogen 
atom from marsh gas, union is effected between the carbon 
atoms. What would result if two hydrogen atoms were to be 
abstracted, and union between the carbons then effected? 
Theoretically we should get a compound made up of two groups 
CH 2 , thus CH 2 .CH 2 , and presumably the relation between the 
carbon atoms in this compound would be different from the 
relation between the carbon atoms in ethane. Without push- 
ing these speculations farther, it may be said that there is a 
well-known hydrocarbon which differs markedly from ethane, 
having the formula C 2 H 4 , and showing the property of unsatu- 
ration very clearly. This is olefiant gas or ethylene. It is the 
first of an homologous series of hydrocarbons, only a very few of 
which, however, are well known. These hydrocarbons yield 
derivatives like the paraffins ; though of these, as well as of the 
hydrocarbons, very few are known as compared with the number 
of the paraffin derivatives. Only a few of them are of much 
importance. 



ETHYLENE. 213 



ETHYLENE AND ITS DERIVATIVES. 

Hydrocarbons, C n H 2n . 

The principal hydrocarbons of this series are included in the 
subjoined table : — 

Ethylene ......... C 2 H 4 . 

Propylene C 3 H G . 

Butylene ......... C 4 H S . 

Ainylene C 5 H 10 . 

Hexylene C^H^. 

Heptylene C 7 H 14 . 

The members are homologous with ethylene. They bear to 
the paraffins a very simple relation, each one containing two 
atoms of hydrogen less than the paraffin with the same number 
of carbon atoms. 

Ethylene, olefiant gas, C 2 H 4 (= CH 2 .CH 2 ). — This gas is 
formed when many organic substances are subjected to dry 
distillation. The two principal reactions which yield it are : — 

(1) The action of an alcoholic solution of potassium hydrox- 
ide on ethyl chloride, bromide, or iodide : — 

C 2 H 5 Br -f KOH = C 2 H 4 + KBr + H 2 0. 

This is the most important reaction for the preparation of the 
unsaturated compounds of the eth}dene series. It is applicable 
not only to the hydrocarbons but to substances belonging to 
other classes. By means of it we have it in our power to pass 
from any saturated compound to the corresponding unsaturated 
compound of the ethylene series. Thus we pass from ethane, 
C 2 H 6 , to ethylene, C 2 H 4 , by first introducing bromine, and then 
abstracting hydrobromic acid from the mono-bromine substi- 
tution-product. By treating the mono-bromine substitution- 



214 UNSATURATED CARBON COMPOUNDS. 

products of other saturated compounds in the same way, the 
corresponding unsaturated compounds can be made. 

(2) The action of sulphuric acid and other dehydrating agents 
upon alcohol : — 

C 2 H 5 .OH = C 2 H 4 + H 2 0. 

Experiment 51. In a flask of 2 1 to 3 1 capacity put a mixture of 
25s alcohol and 150s ordinary concentrated sulphuric acid. Heat to 
160° to 170°, and add gradually through a funnel tube about 500 cc of a 
mixture of 1 part of alcohol and 2 parts of concentrated sulphuric 
acid. Pass the gas through three wash bottles containing, in order, 
sulphuric acid, caustic soda, and sulphuric acid. Then pass it into 
bromine contained in a cylinder, provided with a cork with two holes. 
If the cylinder has a diameter of about 5 cm , let the layer of bromine 
be about 5 cm to 7 cm deep. Upon it pour a somewhat deeper layer of 
w-ter. Place the cylinder in a vessel containing cold water. Pass 
the gas into the bromine until it is completely decolorized. (See note, 
next page.) 

Ethylene is a colorless gas which can be condensed to a 
liquid. It burns with a luminous flame. With oxygen it forms 
an explosive mixture. Its most characteristic property is its 
power to unite directly with other substances, particularly ivith 
the halogens and their hydrogen acids. Thus it unites with 
chlorine and bromine, and with hydriodic and hydrobromic 
acids : — 

C 2 H 4 -f- Cl 2 = C 2 H 4 C1 2 ; 

C 2 H 4 + Br 2 = C 2 H 4 Br 2 ; 

C 2 H 4 + HBr = C 2 H 5 Br ; 

C 2 H 4 + HI = C 2 H 5 I. 

The products formed with chlorine and bromine are called 
ethylene chloride and ethylene bromide. They have been 
mentioned under the head of halogen derivatives of the paraf- 
fins. They are isomeric with ethylidene chloride and ethylidene 
bromide, which are formed by substitution of two hydrogens 
of ethane with chlorine or bromine. 



ETHYLENE. 215 

Note. — The addition of bromine to ethylene is illustrated by the 
experiment last performed, in which ethylene bromide is formed. To 
purify the product, put a little dilute caustic soda in the cylinder, and 
shake. Remove the upper layer of water, and repeat the washing with 
dilute caustic soda. Then wash with water two or three times, each 
time removing the water with the aid of the pipette described on p. 31. 
Finally, put the oil in a flask, add a few pieces of granulated calcium 
chloride, and allow to stand. Pour off into a dry distilling-bulb, and 
distil, noting the temperature. 

A question which we may fairly ask concerning the structure 
of ethylene is this : Does it consist of two groups CH 2 , or of 
a methyl group, CH 3 , and CH ? Is it to be represented by the 
formula CH 2 .CH 2 or CH 3 .CH? Perhaps the clearest answer 
to this question is found in the fact that the chloride formed by 
addition of chlorine to ethylene, and that formed by replacing 
the oxygen in aldehyde by chlorine, are not identical. All 
evidence is in favor of the view that aldehyde is correctly 

represented by the formula CH 3 .Cjj. Hence, as has been 

pointed out, the chloride obtained from it must be represented 
thus, CH 3 .CHC1 2 . Hence, further, it appears highly probable 
that the isomeric chloride obtained from ethylene must be 
represented thus, CH 2 C1.CH 2 C1. Now, as this substance is 
formed by direct addition of chlorine to ethylene, ethylene has 

GH 2 ^iis 

the formula I , and not I 

CH 2 CH 

As regards the relation between the two carbon atoms of 

ethylene we know nothing, save that it is probably different 

from that which exists between the carbon atoms of ethane. 

CH 2 
It is usually represented by the sign = ; thus, || . We must 

CH 2 
necessarily leave the question open as to the relation between 
the carbon atoms in ethylene. If the above sign is used, it 
should serve mainly as an indication of the kind of unsaturation 
met with in ethylene, the compound in whose formula it is 
written having the power to take up two atoms of bromine, a 
molecule of hydrobromic acid, etc. 



216 UNSATURATED CAKBON COMPOUNDS. 

The homologues of ethylene bear the same relation to it that 
the homologues of ethane bear to this hydrocarbon. Propylene 

CH.CH 3 
is methyl-ethylene, I , just as propane is methyl-ethane, 

CH 2 .CH 3 CH 2 CH.CH 3 C(CH 3 ) 2 

I . Butylene is dime thy 1-ethylene, I , or | 

CH 3 CH.C 2 H 5 CH.CH 3 CH 2 

or ethyl-ethylene, I . That is to say, in other words, 

CH 2 

in the hydrocarbons of the ethylene series the ethylene condi- 
tion between carbon atoms occurs only once. 

The higher members of the series need not be considered. 



Alcohols, C n H 2n O. 

These alcohols bear to the ethylene hydrocarbons the same 
relation that the alcohols of the methyl alcohol series bear to 
the paraffins. Only one is well known. This is the second 
member corresponding to propylene. 

Allyl alcohol, C 3 H 6 0(= CH 2 .CH.CH 2 OH). — This alcohol 
is formed in several ways from glycerin. 

1. By introducing two chlorine atoms into glycerin in the 
place of two hydroxy Is, thus getting dichlorhydrin, C 3 H 5 C1 2 . OH : 

CH 2 OH CH 2 C1 

CHOH + 3E? = CHC1 + 2 H 2 ; 

CH 2 OH CH 2 OH 

and treating the dichlorhydrin with sodium, which extracts the 
chlorine : — 

CH 2 C1 CH 2 

I I 
CHC1 + 2 Na = CH + 2 NaCl. 

I I 

CH 2 OH CH 2 OH 



ALLYL MUSTARD OIL. 217 

2. By treating glycerin with the iodide of phosphorus. This 
gives allyl iodide, C 3 H 5 I. By treating the iodide with silver 
hydroxide it is converted into the alcohol. 

3. Most readily by treating glycerin with oxalic acid, as in 
the preparation of formic acid. The mixture is heated to 220° 
to 230°, when allyl alcohol passes over. 

It is manufactured in this way on the large scale for the pur- 
pose of making artificial oil of mustard. The reactions involved 
are quite complicated. 

Allyl alcohol is a liquid boiling between 96° and 97°. It has 
a penetrating odor. 

Nascent hydrogen does not act upon it, or at least the action, 
if any, takes place with difficult}'. As far as composition is 
concerned, the relation between allyl alcohol and propyl alcohol 
is the same as that between ethylene and ethane : — 

C 3 H 3 . OH -f H 2 = C 3 H 7 . OH. 

Allyl alcohol, like ethylene, unites directly with bromine, 
hydrobromic acid, etc., the products being substitution-products 
of propyl alcohol : — 

C 3 H 5 .OH + HBr = C 3 H 6 Br.OH, 

Monobrom-propyl alcohol. 

C 3 H 5 .OH + 2 Br = C 3 H 5 Br 2 .OH. 

Dibrom-propyl alcohol. 

Allyl compounds. — Among the derivatives of allyl alco- 
hol which are of special interest is allyl sulpiride, (C 3 H 5 ) 2 S, 
which is the chief constituent of the oil of garlic. It can be 
made artificially by treating allyl iodide with potassium sul- 
phide : — 

2C 3 H 5 I + K 2 S = (C 3 H 5 ) 2 S + 2KI. 

It is an oily liquid of a disagreeable odor. 

Allyl mustard oil, SON. C 3 H 5 . — Under the head of 
Sulpho-cyanates mention was made of a series of isomeric 
bodies called isosulpho-cyanates or mustard oils. The sulpho- 



218 UNSATURATED CARBON COMPOUNDS. 

cyanates of the alcohol radicals are made from potassium 
sulpho-cyanate. Thus, methyl sulpho-cyanate is made by 
mixing together potassium methyl-sulphate and potassium 
sulpho-cyanate, and distilling : — 

NCSK + C ^ 3 °}s0 2 = K 2 S0 4 + NCSCH 3 . 

The mustard oils, on the other hand, are made by a compli- 
cated reaction from carbon disulphide and substituted ammonias. 
The conduct of the sulpho-cyanates led us to the conclusion 
that they must be represented by the formula NC — SR, while 
that of the isosulpho-cyanates or mustard oils led to the for- 
mula SC — NR, as representing their structure. Allyl mustard 
oil is the chief representative of the class of bodies known 
as mustard oils. It occurs as a glucoside (see p. 180) in 
mustard seed. From the glucoside it is formed by fermenta- 
tion. It is formed by treating allyl iodide with potassium 
sulpho-cyanate. We should naturally expect this reaction to 
yield allyl sulpho-cyanate, but the compound actually obtained 
does not conduct itself like the sulpho-cyanates. 

AII3I mustard oil is a liquid, boiling at 150.7°, and having a 
penetrating odor. 

With zinc and hydrochloric acid it is converted into allyl- 
amine, NH 2 .C 3 H 5 , hydrogen sulphide and carbon dioxide. This 
reaction indicates that in allyl mustard oil the radical allyl is in 
combination with the nitrogen and not with the sulphur. 

Note for Student. — What change do the mustard oils in general 
undergo when treated with nascent hydrogen? What change do the 
sulpho-cyanates undergo when oxidized ? 

Acrolein, acrylic aldehyde, 3 H 4 O(= C 2 H 3 .COH). — Acro- 
lein can be made by careful oxidation of allyl alcohol. It is 
formed by the dry distillation of glycerin which breaks up into 
water and acrolein : — 

C 3 H 8 3 = C 3 H 4 -f- 2 H 2 0. 



acids, C n H 2n _ 2 2 . ' 219 

It is, hence, formed also by heating the ordinary fats, the 
peculiar penetrating odor noticed when fatty substances are 
heated to a sufficiently high temperature being due to the forma- 
tion of acrolein. It is prepared best by heatiug glycerin with 
acid potassium sulphate. 

Experiment 52. In a test-tube mix anhydrous glycerin (I part) 
and acid potassium sulphate (2 parts) , and heat the mixture. Pass 
the vapors through a bent tube into water contained in another test- 
tube. Notice the odor. Try the effect on a dilute solution of nitrate 
of silver. What is the meaning of this reaction? 

Acrolein is a volatile liquid which boils at 52.4°. It has an 
extremely penetrating odor, and its vapor acts violently upon 
the eyes, causing the secretion of tears. 

Acrolein takes up oxygen from the air, and is converted into 
the corresponding acid, acrylic acid, C 3 H 4 2 (which see) . 

It takes up hydrogen, and is thus converted into allyl alcohol. 

It takes up hydrochloric acid, and is converted into /5-chlor- 
propionic aldehyde : — 

C 2 H 3 .COH + HC1 = CH 2 C1.CH 2 .C0H. 

/3-chlor-propionic aldehyde. 

The first two reactions are characteristic of aldehydes in 
general ; the last one is characteristic of unsaturated compounds 
belonging to the ethylene group. Acrolein, like ordinary alde- 
hyde, forms polymeric modifications, which can easily be recon- 
verted into acrolein. 

It unites with ammonia forming acrolem-ammonia, and with 
other substances in much the same way as ordinary aldehyde 
does. 

Acids, C n H 2n _ 2 2 . 

Running parallel to the ethylene series of hydrocarbons, and 
bearing the same relation to it that the fatty acid series bears 
to the paraffins, is a series of acids of which the first member 
is acrylic acid, C 3 H 4 0,. Several members of the series are 



220 UNSATURATED CARBON COMPOUNDS. 

known. The principal members are named in the subjoined 
table : — 

ACRYLIC ACID SERIES. 
Acids, C n H 2n _ 2 2 . 

• Acrylic acid ...... C 3 H 4 2 . 

Crotonic " C 4 H 6 2 . 

Angelic " C 5 H 8 2 . 

Hydrosorbic u C 6 H 10 O 2 . 

Teracrylic " QHjA- 

Cimic " C 15 H 28 2 . 

Hypogseic " C 16 H 30 O 2 . 

Oleic " . . \ ... C^H^Os. 

Erucic " C22H42O2. 



Of most of the higher members of the series several isomeric 
modifications are known. Only a few of these acids will be 
considered here. 

Acrylic acid, C 3 H 4 O 2 0= 0H..CH.CO 2 H). — This acid has 
already been mentioned in connection with hydracrylic acid, 
which, when heated, breaks up into acrylic acid and water : — 

CH 2 .OH.CII 2 .C0 2 H = CH 2 .CH.CO,H + H 2 0. 

Hydracrylic acid. Acrylic acid. 

Note for Student. — This reaction is analogous to that which 
takes place when ordinary alcohol is converted into ethylene. In what 
does the analogy consist? What acid is isomeric with hydracrylic 
acid? How does it conduct itself when heated? Compare the trans- 
formation of hydracrylic acid into acrylic acid with that of malic into 
male'ic and f umaric acids, and with that of citric into aconitic acid. 

Acrylic acid can be made by careful oxidation of acrolein 
with silver oxide. The relations between propylene, C 3 H 6 , 



OLEIC ACID. 221 

allyl alcohol, C 3 H 5 .OH, acrolein, C 2 H 3 .COH, and acrylic acid, 
C 2 H 3 .C0 2 H, are the same as those between any hydrocarbon of 
the paraffin series, and the corresponding primary alcohol, 
aldehyde, and acid. 

Acrylic acid can be made further by treating /?-iodo-propi- 
onic acid with alcoholic potash : — 

CHJ .CH 2 .C0 2 H = CH 2 .CH .C0 2 H + HI. 

Note for Student. — Compare this reaction with that by which 
ethylene is made from ethyl bromide. 

Acrylic acid is a liquid having a pungent odor. It boils at 
140°, and solidifies at a low temperature. 

Nascent hydrogen converts it into propionic acid. Hydri- 
odic acid unites directly with it, forming /?-iodo-propionic acid. 

Note for Student. — What are the analogous reactions with allyl 
alcohol and acrolein? 

Many derivatives of acrylic acid have been studied, but they 
need not be taken up here. 

Crotonic acid, C JI 6 2 . — Crotonic acid is made from allyl 
cyanide, the reactions involved being represented by the 
following equations : — 

C 3 H 5 I + KCN = C 3 H 5 .CN -f KI ; 

Allyl iodide. Allyl cyanide. 

C 3 H 5 .CN + 2H 2 = C 3 H 5 C0 2 H + NH 3 . 

Crotonic acid. 

It can be made also by distilling /?-lrydroxy-butyric acid, 
CH 3 .CH(OH).CH 2 .C0 2 H, when a reaction takes place similar 
to that involved in the preparation of acrylic from hydracylic 
acid. Further, it can be made by treating a-brom-butyric acid 
with alcoholic potash. 

Oleic acid, C^H^C^. — This acid was spoken of in con- 
nection with the fats, it being one of the three acids found 



222 UNSATURATED CARBON COMPOUNDS. 

most frequently in combination with glycerin. Olei'n, or 
glyceryl tri-oleate, is the liquid fat, and is the chief constituent 
of the fatty oils, such as olive oil, whale oil, etc. It is con- 
tained also in almost all ordinary fats. In the preparation of 
stearic acid for the manufacture of candles, the olein is pressed 
out of the fats. To prepare the acid, olei'n is saponified, and 
the soap then decomposed with lrydrochloric acid. 

Note for Student. — Give the equations representing the reac- 
tions involved in passing from olein, or glyceryl tri-oleate, to oleic acid. 

Oleic ticid is a crystallized substance which melts at a low 
temperature (14°). It unites with bromine, forming dibrom- 
stearic acid. Hydriodic acid converts it into stearic acid : — 

C18H34O2 -+■ H 2 = C 18 H3g0 2 . 

Oleic acid. Stearic acid. 

Polybasic Acids of the Ethylene Group. 

There are a few dibasic acids which bear to the ethylene 
hydrocarbons the same relations that the members of the oxalic 
acid series bear to the paraffins. They may be regarded as 
derived from the hydrocarbons by the introduction of two 
carboxyl groups. 

Acids, C 2 H 2 (C0 2 H) 2 . — There are two acids of this for- 
mula, both of which have been mentioned. They are fumaric 
and male'ic acids, which are formed by the distillation of malic 
acid. 

Fumaric acid can also be made by treating brom-succinic 
acid with alcoholic potash. 

Both fumaric and male'ic acids are converted into succinic 
acid by nascent hydrogen, and into brom-succinic acid by 
hydrobromic acid. It is believed that these two acids are 
stereo-isomeric, and that the following formulas suggest the 
relation between them : — 



ACETYLENE AND ITS DERIVATIVES. 223 

HC.C0 2 H HC.C0 2 H 

II i II 

HC.C0 2 H C0 2 H.CH 

Malei'c acid. Fumaric acid. 

Each of the carbon atoms which are united by double lines is sup- 
posed to be at the centre of a tetrahedron, and the two tetrahedrons 
to be united in such a way that they have one edge in common. 

Acids, C 5 H 6 4 . — There are three acids of this formula, all of 
which are obtained, either directly or indirectly, from citric acid. 
They are known as itaconic, citraconic, and mesaconic acids. 

CO H 
They bear the same relation to pyrotartaric acid, C 3 H 6 < 2 , 

that fumaric and malei'c acids bear to succinic acid. All are con- 
verted into pyrotartaric acid by treatment with nascent hydrogen. 

Aconitio acid, [0 6 H 6 O 6 (= C 3 H: S (C0 2 H) 3 )]. — Aconitic acid is 
the only tri-basic acid of this group that need be mentioned. 
As has been stated, it is formed when citric acid is heated to 
175°. It is found in nature in aconite root, and in the sap of 
sugar-cane and of the beet. 

Nascent hydrogen converts it into tri-carballylic acid, 
C 3 H 5 (C0 2 H) 3 . 

Acetylene and its Derivatives. 

The principal reactions by means of which we are enabled to 
pass from a hydrocarbon of the paraffin series to the corre- 
sponding hydrocarbon of the ethylene series consist in intro- 
ducing a halogen into the paraffin, and then treating the 
mono-halogen substitution-product with alcoholic potash : — 

C 2 H 5 Br = C 2 H 4 + HBr. 

The effect of these two reactions is the abstraction of two 
hydrogen atoms from the paraffin. The following questions 
therefore suggest themselves : — 

Suppose a dibrom substitution-product of a paraffin be heated 



224 UNSATURATED CARBON COMPOUNDS. 

with alcoholic potash ; will the effect be that represented by 
the equation 

C 2 H 4 Br 2 = C 2 H 2 + 2HBr? 

And, further, suppose a mono-substitution product of an 
ethylene hydrocarbon be treated with alcoholic potash ; will the 
effect be that represented by the equation 

C 2 H 3 Br = C 2 H 2 + HBr? 

If so, it is plain that we have it in our power to make a new 
series of hydrocarbons, the members of which must bear to the 
ethylene hydrocarbons the same relation that the latter bear to 
the paraffins. The general formula of tjiis series would be 
C n H 2n _ 2 , that of the ethylene series being CnH^, and that of the 
paraffin series, C n H 2n+2 . 

A few members of. the hydrocarbon series, C n H 2n _ 2 , are 
known, though only one is well known, and this one alone need 
be considered. 

Acetylene, C 2 H 2 . — Acetylene is formed by direct combina- 
tion of hydrogen and carbon when a current of lrydrogen is 
passed between carbon poles, which are incandescent in conse- 
quence of the passage of an electric current ; when alcohol, 
ether, and other organic substances are passed through a tube 
heated to redness ; when coal gas and some other substances 
are burned in an insufficient supply of air ; and when ethylene 
bromide is treated with alcoholic potash : — 

C 2 H 4 Br 2 = C 2 H 2 + 2 HBr. 

It can be prepared most conveniently by the incomplete com- 
bustion of coal gas. 

Experiment 53. — Light a Bunsen burner at the base, and turn it 
down so that the flame is small. The condition is the same as that 
observed when a burner "strikes back." The odor noticed, which is 
familiar to every one who has worked in a chemical laboratory, is 
that of acetylene, which is mixed with the products given off from 



ACETYLENE. 



225 



the burner. To collect the gas, arrange an apparatus as shown in 
Fig 13. The brass tube A is screwed to the burner, which is lighted 
at the base. In B is a stong solution of ammoniacal cuprous chlo- 
ride prepared as follows : Make a saturated solution of 1 part com- 
mon salt and 2} parts crystallized copper sulphate. Saturate with 
sulphur dioxide. Filter, and wash with acetic acid. Dissolve the 
white cuprous chloride in ammonia. 




Fig. 13. 



Connect the apparatus at C with some kind of aspirator (suction- 
pump, a gasometer filled with water, etc.), and draw the gases slowly 
through the solution. The acetylene will be absorbed by the copper 
solution, and a precipitate formed (see Exp. 54). 



Acetylene is a gas of an unpleasant odor. It burns with a 
luminous, sooty flame. 

When heated to a sufficiently high temperature, it is con- 
verted into the polymeric substances, benzene, C 6 H 6 , and sty- 
rene, C 8 H 8 . It unites with hydrogen to form ethylene and 



226 UNSATURATED CARBON COMPOUNDS. 

ethane. It unites with nitrogen, under the influence of the 
sparks from an induction coil, forming hydrocyanic acid: — 

C 2 H 2 + 2N = 2 HCN. 

Acetylene forms some curious compounds with metals and 
metallic oxides. Among them may be mentioned the copper 
compound obtained in Exp. 53. This has the composition, 
C 2 Cu 2 , which represents the cuprous salt of acetylene. It is 
a reddish-brown substance which is insoluble in water. When 
dry, it explodes violently at 120°. Hydrochloric acid decom- 
poses it, acetylene being evolved. 

Experiment 54. Filter off the precipitate obtained in Exp. 53, 
and wash it until the wash-water runs through colorless. Bring the 
precipitate, together with a little water, into a flask furnished with a 
funnel-tube and a delivery-tube. Slowly acid concentrated hydro- 
chloric acid, and notice the evolution of gas. Collect some of it 
in a small cylinder over water, and burn it. 

Acetylene unites with bromine, forming the compound 
C 2 H 2 Br 4 , tetra-brom-ethane. It unites with hydrobromic and 
hydriodic acids, forming substitution-products of the satu- 
rated hydrocarbons : — 

(^ 2 xl 2 -f- u HI = v^H^Ijj. 

Most of the higher members of the acetylene series of hydro- 
carbons bear to acetylene the same relation that the higher mem- 
bers of the ethylene series bear to ethylene. The first one is 

C.CH 3 

Allylene or methyl-acetylene . . . . | ; 

the second is 

C.C 2 H 5 

Ethyl- acetylene I , 

CH 

C.CH 3 

or Dimethyl-acetylene | 

C.CH 3 






PBOPAHGrYL ALCOHOL. 227 

It should be noticed in this connection that there is a hydro- 
carbon of the formula C 4 H 6 , which, strictly speaking, is not 
a homologue of acetylene, though it is very closely allied to 

CH = CH 2 
dimethyl- acetylene. It has the formula I 

CH = CH 2 

The homologues of acetylene may be divided into two 
classes : — 

1. Those which are obtained from acetylene by the replace- 
ment of one or both the hydrogen atoms by saturated radicals, 
such as methyl, ethyl, etc. These may be called the true homo- 
logues. They all retain the condition peculiar to acetylene. 

2. Those in which the ethylene condition occurs twice, as in 
the hydrocarbons of the formulas 

CH = CH 2 C(CH 3 ) 2 

I , || , etc. 

OH = O-U2 ^ == OH2 

These may be called (Methylene derivatives. 

We know nothing regarding the relation between the carbon 
atoms in acetylene. It is commonly represented by three lines 

CH 

( = ),or three dots ( : ). Thus, acet} T lene is written ill or CHjCH. 

CH 
Like the sign for the ethylene condition, it should not be inter- 
preted too literally. It is best to regard it as the sign of a 
condition best illustrated in acet}dene, and which may therefore 
be called the acetylene condition. We recognize this condition in 
a compound by the power of the compound to take up four atoms 
of a halogen, or two molecules of hydrobromic acid and similar 
acids; though, as we have seen, these reactions are not distinc- 
tive for the acetylene condition, for the reason that the diethy- 
lene compounds have the same power. 

Propargyl alcohol, 3 H 4 O. — This alcohol is mentioned 
merely as an example of alcohols which are derived from the 
acetylene hydrocarbons. It is the hydroxy 1 derivative of 



228 UNSATURATED CARBON COMPOUNDS. 

allylene, or methyl-acet3"lene. It is made by treating brom- 
allyl alcohol, C 3 H 4 Br.OH, with alcoholic potash : — 

C 3 H 4 Br.OH = C3H3.OH + HBr. 

Acids, C n H 2n _ 4 2 . 

These acids are the carboxyl derivatives of the acetylene 
hydrocarbons, and hence differ from the members of the 
acrylic acid series by two atoms of Irydrogen each, and from 
the members of the fatty acid series by four atoms of hydro- 
gen each. 

/ CH \ 

Propiolic acid, C 3 H 2 2 ( = | ]. — The bromine and 

V C.C0 2 H/ 
chlorine substitution-products of this acid are more easily made 
and are better known than propiolic acid itself. Chlor-propio- 
lic acid is obtained by treating dichlor-acrylic acid with baryta 
water : — 

C 2 HC1 2 .C0 2 H = C 2 C1.C0 2 H + HC1-. 

/ O.OHs \ 
Tetrolic acid, 4 H 4 O 2 ( = I J, is obtained by treating 

/S-chlor-crotonic acid with caustic potash : — 

CCI.CH3 C.CH 3 

I = I + HC1. 

CH.C0 2 H C.C0 2 H 

Sorbic acid, C c H s 2 (^ C 5 H T .C0 2 H). — This acid occurs in 
the unripe berries of the mountain ash. It takes up hydrogen 
and yields hydrosorbic acid, a member of the acrylic acid series 
(see table, p. 220). It also takes up bromine, the final product 
of the action being an acid of the formula C 5 H 7 Br 4 .C0 2 H. With 
hydrobromic acid it forms dibrom-caproic acid : — 

C 5 H 7 .C0 2 H + 2 HBr = C 5 H 9 Br 2 .C0 2 H. 

Dibrom-caproic acid. 



DIPBOPARGYL. 229 

Leinoleic acid, C 16 H 28 2 (= C 15 H 27 .C0 2 H). — This acid occurs 
in the form of an ethereal salt of glycerin in linseed oil. It can 
be obtained from linseed oil by saponification. It is an oily 
liquid, one of the most marked properties of which is its power 
to take up oxygen from the air, it being thus transformed into a 
solid substance. Linseed oil itself has this property of harden- 
ing or drying. It is the principal substance belonging to the 
class of drying oils. The oil is used extensively as a constituent 
of varnishes and of oil paints. 



Valylene, C 5 H C . — We have thus far had to deal with three 
series of hydrocarbons of the general formulas C n H 2n + 2 , C n H 2n , 
and C n H 2n _ 2 . We naturally inquire whether there is a series of 
the general formula C n H 2n _ 4 . A few members of the series have 
been prepared by abstracting hydrogen from certain of the acety- 
lene hydrocarbons by the action of alcoholic potash on the bro- 
mine derivatives. Thus, valylene, C 5 H 6 , has been made by 
treating valerylene bromide, C 5 H 8 Br 2 , with alcoholic potash : — 

C 5 H 8 Br 2 = C 5 H 6 + 2 HBr. 

It is a liquid. Its most characteristic property is its power to 
unite with bromine to form the saturated compound C 5 H 6 Br 6 . 

Dipropargyl, C 6 H 6 . — Dipropargyl is obtained from the 
compound dibrom-diallyl, C 6 H 8 Br 2 , by boiling with alcoholic 
caustic potash : — 

C 6 H 8 Br 2 = C 6 H 6 -f- 2 HBr. 

It unites very readily with bromine, forming, as the final 
product of the action, the compound C 6 H 6 Br 8 , which is an 
octo-bromine substitution-product of hexane, C 6 H 14 . 



The unsaturated hydrocarbons and their derivatives thus far 
considered are obtained by simple reactions from the saturated 



230 UNSATURATED CARBON COMPOUNDS. 

compounds, and they all have the power to take up readily 
bromine, hydrobromic acid, etc., and thus to pass back to the 
saturated condition. Whatever the real nature of the relation 
between the carbon atoms in all these unsaturated hydrocarbons 
may be, it certainly is easily changed to the condition which 
exists in the saturated compounds. There are several hydro- 
carbons, however, which are unsaturated but which are not 
easily converted into derivatives of the saturated hydrocar- 
bons. Although under some circumstances they with diffi- 
culty unite directly with the halogens, they do not take up 
enough to convert them into derivatives of the paraffins ; and 
the products which are formed are unstable, easily giving up 
the halogen atoms with which they united. The simplest 
hydrocarbon of this new kind is the well-known benzene, 
which is isomeric with dipropargyl. Before proceeding to 
the consideration of benzene and its derivatives, it will be 
well to inquire whether the abstraction of hydrogen by the 
reaction chiefly used can be pushed further than it has thus 
far been pushed. Can we, in other words, by means of this 
reaction get hydrocarbons of the formula C n H 2n _ 8 which have 
the power to unite directly with ten atoms of bromine? Such 
hydrocarbons have not been prepared. Hydrocarbons of the 
formula C n H 2n _ 8 are known ; but they are not made from the 
paraffins b} T abstracting hydrogen, and they are not converted 
into substitution-products of the paraffins b} T the addition of 
halogens and halogen acids. The compounds which have 
been considered fall under five general heads, according to the 
formulas of the hydrocarbons. These heads are, — 

1. Hydrocarbons, C n H 2n + 2 , the paraffins and their derivatives. 

2. Hydrocarbons, C n H 2n , or olefins and their derivatives. 

3. Hydrocarbons, C n H 2n _ 2 , or the acetylene hydrocarbons and 

their derivatives. 

4. Hydrocarbons, C n H 2n _ 4 , and their derivatives. 

5. Hydrocarbons, CJET^.e, and their derivatives. 



GENERAL CONSIDERATIONS. 231 

This classification, while strictly correct, is misleading, inas- 
much as it conveys no idea in regard to the relative importance 
of the compounds of the different classes. As we have seen, 
the only compounds whose treatment required much time are 
those of the first class. These compounds stand out promi- 
nently, and are distinguished by the frequency of their occur- 
rence and their great number. The compounds of the second 
class are much less numerously represented, and but a small 
number of them are familiar substances. While a few sub- 
stances belonging to the third class are known, our knowledge 
in regard to the class is much more limited than even that 
of the second class. Finally, as regards the fourth and fifth 
classes, the few representatives of them that are known are at 
present scientific curiosities. Thus, after we leave the paraffin 
derivatives, our knowledge dwindles away very rapidly when 
we pass to the following classes, until it ends with a single 
compound in the fifth class. 

We pass now to the consideration of a new group, the impor- 
tance and number of whose members entitle it to be placed side 
by side with the group of paraffin derivatives. 



CHAPTER XIV. 

THE BENZENE SERIES OP HYDROCARBONS.- 
AROMATIC COMPOUNDS. 

The fundamental substance of this group is benzene, C 6 H 6 , 
which bears to the group the same relation that marsh gas 
bears to the group of paraffin derivatives. Benzene, together 
with some of its homologues, is a product of the distillation of 
bituminous coal, and is, therefore, contained in coal tar. As 
coal tar is the raw material from which all benzene derivatives 
are obtained, it will be well briefly to consider the conditions 
of its formation and the method of obtaining pure hydrocarbons 
from it. 

Coal tar is a thick, black, tarry liquid, which is obtained in 
the manufacture of illuminating gas from bituminous coal. 
The coal is heated in retorts, and all the products passed 
through a series of tubes called condensers. These are kept 
cool, and in them the liquid and volatile solid products are con- 
densed, forming together the coal tar. It is an extremely com- 
plex mixture, from which a great many substances have been 
obtained. Among those most readily obtained from it are the 
hydrocarbons of the benzene series, as well as the hydrocarbons 
naphthalene and anthracene, both of which are important sub- 
stances. 

When the tar is heated, of course the most volatile liquids 
pass over first. These are collected in vessels containing water. 
The first portions of the distillate float on water, and constitute 
what is called the light oil. After a time hydrocarbons and 
other substances of greater specific gravity than the light oil 



BENZENE SERIES. 233 

pass over. These portions sink under water, and constitute the 
heavy oil. 

The light oil is treated with caustic soda, which removes 
phenol (carbolic acid) and similar substances, and with 
sulphuric acid, which removes certain basic compounds. The 
residue is then subjected to fractional distillation, by which 
means the first two members of the series can be obtained in 
very nearly pure condition. As these hydrocarbons form the 
basis of a number of important industries, they are separated 
from coal tar on the large scale. 

The principal members of the series are named in the table 
below. 

HYDROCARBONS, C n H 2n -6. 
Benzene Series. 

Benzene C 6 H 6 . 

Toluene C 7 H 8 . 

Xylene C 8 H 10 . 

Mesitylene ) p tt 

Pseudocumene ) 

Durene } n tt 

Cymene ) 

Hexa-methyl benzene C 12 H 18 . 

Benzene, C 6 H 6 . — Benzene is prepared, as above described, 
from the light oil obtained from coal tar. It is also prepared 
by heating benzoic acid with lime, when the acid breaks up 
into carbon dioxide and benzene : — 

C 7 H 6 2 = C/ 6 H 6 -f- C0 2 . 

Note for Student. — What is the analogous method for the 
preparation of marsh gas? 

Benzene has been made further by simply heating acetylene : 

O i_^2-ti 2 = l^gtig. 



234 BENZENE SERIES OF HYDROCARBONS. 

To purify the hydrocarbon obtained by fractional distillation 
from light oil, it is cooled down to a low temperature, and that 
which does not solidify is poured off. The crystals are pressed 
in the cold between layers of bibulous paper, and are then very 
nearly pure benzene. This can be further purified by treat- 
ment with sulphuric acid, which removes a small quantity of a 
substance containing sulphur, and known as thiophene. Per- 
fectly pure benzene is obtained by distilling pure beDzoic acid 
with lime. 

Experiment 55. Mix intimately 50s benzoic acid and 100? quick- 
lime, and distil from a flask connected with a condenser. See that the 
materials and apparatus are dry. Add a little calcium chloride to the 
distillate ; and, after it has stood for an hour or two, redistil it from 
an appropriate sized distilling-bulb, noting the temperature at which it 
boils. Put the redistilled hydrocarbon iu a test-tube, and surround it 
with a freezing mixture. 

Experiment 56. — In most places where there are gas-works it will 
not be difficult to get a quantity of light oil. The separation of some 
of this into benzene and toluene, and the purification of the two hydro- 
carbons, is the best possible introduction to a study of the aromatic 
compounds. The benzene and toluene thus obtained may be used in the 
preparation of a number of typical derivatives according to methods 
which will be described. In f ractioning the light oil, it will be observed 
that there is a tendency to an accumulation of the distillates in the 
parts boiling near 80° (the boiling-point of benzene) and 110° (the boil- 
ing-point of toluene). The final purification of the benzene should be 
effected by freezing and pressing, as described above. The toluene 
should be distilled until by redistillation its boiling-point is not changed. 

Benzene is a colorless liquid which boils at 80.5°. It has a 
peculiar, pleasant odor. Several of the homologues of benzene 
have a similar odor. Hence the name aromatic compounds was 
given to them originally, and it is still in general use. Benzene 
is lighter than water, its specific gravity being 0.899 at 0°. It 
burns with a bright, luminous flame. 

Experiment 57. — Pour a layer of benzene on water in a small 
evaporating-dish. Set fire to it. 



BENZENE. 235 

At 0° benzene solidifies, forming rhombic prisms. It is an 
excellent solvent for oily and resinous substances. 1 

Chemical conduct of benzene, and hypothesis regarding its 
structure. In the light of the knowledge we have already 
gained in studying hydrocarbons which contain a smaller pro- 
portion of hydrogen than the paraffins do, we should naturally 
expect to find that benzene can easily be converted into a 
derivative of hexane. We should naturally expect to find 
that it unites with bromine, just as dipropargyl does, to 
form an octo-brom-hexane thus, — 

C 6 H 6 + Br 8 = C 6 H 6 Br 8 ; 

with hydrobromic acid to form tetra-brom-hexane thus, — 

C a H 6 + 4HBr = C 6 H 10 Br 4 ; 

and probably with hydrogen to form hexane, — 

C&Rq + 8H = C 6 H 14 . 

But none of these reactions takes place. Hydrobromic acid, 
which acts so readily on all the unsaturated compounds hitherto 
considered, does not act at all upon benzene. Bromine acts 
readily enough, but the action which usually takes place is 
like that which takes place with the saturated paraffins. It is 
substitution, and not addition. Thus, bromine forms mono- 
brom-benzene, C 6 H 5 Br, under ordinary circumstances. If, 
however, the action takes place in the direct sunlight, a prod- 
uct is formed which has the formula C 6 H 6 Br 6 , known as 
benzene hexabromide, and to this no more bromine can be 
added. Further, benzene hexabromide is an unstable com- 
pound, — much less stable than benzene. When heated, it 
breaks up, partly according to the equation 

C 6 H 6 Br 6 = C 6 H 3 Br 3 + 3 HBr, 

1 Benzene, the chemical individual of the definite formula C 6 H G , must not be con- 
founded with "benzine," the commercial substance obtained in the refining of petro- 
leum (see p. 110). 



2BG BENZENE SERIES OF 11YDFOCAHBONS. 

the chief product being a substitution-product of benzene, — 
tri-brom-benzene, C 6 H 3 Br 3 . 

Treated with hydriodie acid, benzene takes up six atoms of 
hydrogen, and yields a hydrocarbon, CgH^, which, however, does 
not act like a member of the ethylene series, as it appears to 
have no power to take up bromine, etc., and shows a marked 
tendency to pass back into benzene, particularly under the influ- 
ence of oxidizing agents. 

The facts mentioned show clearly that benzene differs in some 
way fundamentally from all the hydrocarbons which have been 
considered. But these facts are not sufficient to enable us to 
form an hypothesis in regard to its structure. On studying the 
many substitution-products of benzene, however, we soon become 
acquainted with facts of a different order and of the highest im- 
portance. 

It will be remembered that the theory in regard to the rela- 
tions of the paraffins to each other is based upon the fact, that 
only one mono-substitution product of marsh gas can be obtained 
with any given substituting agent. There is but one chlor- 
methane, but one brom-methane, etc. This fact leads us to 
believe that each hydrogen atom of marsh gas bears the same 
relation to the carbon atom, or that marsh gas is a s3-mmetrical 
compound. A similar conclusion has been reached in regard to 
benzene ; and it is based upon a most exhaustive study of the 
substitution-products. Notwithstanding almost innumerable 
efforts to prepare isomeric mono-substitution products of ben- 
zene, no such isomeric substances have been prepared. There 
is but one mono-brom-benzene, but one mono-chlor-benzene, 
etc., etc. Further, mono-brom-benzene has been prepared by 
replacing the six hydrogen atoms of benzene successively by 
bromine ; and the product has been found to be the same, no 
matter which hydrogen is replaced. As this fact is of funda- 
mental importance, it will be well to consider how it is possible 
to replace the six hydrogens successively, and to know that in 
each case a different hydrogen atom is replaced. While it would 



BENZENE. 237 

ieiid us too far to follow this subject in detail, the principle 
made use of can be made clear in a few words : — 

We have a compound, the formula of which is C 6 H 6 . Write 

12 3 4 5 6 

it thus, C 6 HHHHHH, numbering the hydrogen symbols to facil- 

1 
itate reference to them. The problem is to replace, say H, by 

2 

bromine ; in a second case, to replace H by bromine ; in a 

3 

third, H, etc ; and to compare the six mono-brom-benzenes thus 
obtained. Suppose we treat benzene with bromine. We get 
a mono-brom-benzene, and we kuow that one of the hydrogen 
atoms is replaced by bromine, but of course we cannot tell 
which one. We may assume that it is any one of the six 
represented in the above formula. For the sake of the argu- 

1 2 3 4 5 6 

ment, call it H. Our compound is therefore C 6 BrHHHHH. 
Now treat this compound with something else which has the 
power to replace the hydrogen, say nitric acid. A second 
hydrogen atom is replaced by the nitro group N0 2 . Again, 
we do not know which one of the hydrogen atoms is replaced 
in this operation, but ive do know that it is a different one 
from that ivhich ivas replaced by the bromine in the first 

2 

operation. Call it H. We have, therefore, the compound 

3 4 5 6 

C 6 Br(N0 2 )HHHH. By treating this compound with nascent 

hydrogen, two reactions take place, the chief one for our 

present purpose being the replacement of the bromine by 

i 
hydrogen. In other words, H is put back into the com- 

1 3 4 5 6 

pound again, and we have C 6 H(N0 2 )HHHH. By means 
of two reactions which will be studied farther on it is a 
simple matter to replace the nitro group by bromine. This 

1 3 4 5 6 

done, we have the compound C 6 HBrHHHH, or a mono-brom- 
benzene, in which the bromine certainly replaces a different 
hydrogen atom from that replaced by direct substitution. The 
two products are, however, identical. The above explanation 
will serve to make the principle clear which is involved in the 



238 BENZENE SERIES OF HYDROCARBONS. 

study of the relations which the hydrogen atoms contained in 
benzene bear to the molecule. The principle has been applied 
successively to all the hydrogen atoms, and, as already stated, 
the result is the proof that all these hydrogen atoms bear the 
same relation to the molecule. 

Thus far we have formed no conception in regard to the rela- 
tions existing between the constituents of benzene. Can we, 
on the basis of the facts above stated, form any satisfactory 
conception in regard to these relations? How can we imagine 
six carbon atoms and six hydrogen atoms arranged so that all 
the latter shall bear the same relation to the molecule? The 
simplest conception is that each carbon is in combination with 
one hydrogen, and that the six carbon atoms are arranged in 
the form of a ring, and not, as in the paraffins, in the form of 
an open chain, or a chain with branches. Using our ordinary 
method of representation, this conception is symbolized in the 
formula 




or, as the curved lines have no special significance, the expres« 



sion becomes 



H 
HCT X CH 

I I 

HC X /CH 

x cr 



This symbol, then, is the expression of a thought which is 
suggested by a study of the chemical conduct of benzene. 



BENZENE. 239 

Before we can accept it as probable, it must first be tested by 
all the facts known to us. If it is not in accordance with all of 
them, if it suggests possibilities which are not realized, then it 
must be discarded, and we must form some other conception in 
regard to the structure of benzene. 

In the first place, then, does it account for the addition 
products, benzene hexabromide, hexa-hydro-benzene, etc. ? The 
formula represents each carbon atom as trivaleut, and we should 
expect, therefore, that each one could take up an additional 
univalent atom, forming, in the case of bromine, a compound 
of the formula HBr 

BrHC X x CHBr 

I i 

BrHC x /CHBr 

HBr 

in which each carbon atom is acting as a quadrivalent atom. 
Unless the ring form of combination between the carbon atoms 
is broken up, it is impossible for the compound to take up more 
bromine. Hence, the last product of the addition of bromine 
to benzene should be benzene hexabromide ; and, in the same 
way, the last product of the addition of hydrogen should be 
hexa-hydro-benzene, as it is. The facts and the hypothesis are 
in harmony. 

Again, we may inquire : Of how many isomeric di-substitu- 
tion products of benzene does the hypothesis suggest the exist- 
ence? Numbering the hydrogens in the formula, we have : — 

(1)H 

(6)HC / X CH(2) 

I I 

(5)HC X /CH(3) 

x cr 

H(4) 
The hydrogens (1) and (2), (2) and (3), (3) and (4), (4) and 



240 BENZENE SERIES OF HYDEOCAEBONS. 

(5), (5) and (6), and (6) and (1), bear the same relations to 
each other ; and, according to the formula, whether we replace 
(1) and (2), or (2) and (3), or (3) and (4), or any other of 
the above-named pairs, the product ought to be the same. We 
should get a compound of which the following is the general 
expression, in which X represents any substituting atom or 
group : — x 

HC X X CX 

I I 

HC s. / CH 

x cr 

H 

Formula I. 

« 

In the second place, the hydrogens (1) and (3), (2) and 
(4), (3) and (5), (4) aud (6), (5) and (1), and (6) and (2) 
bear to each other the same relation, but a different relation 
from that which the above pairs do. Replacing any such pair, 
we should have a second compound, which is represented by 
the general formula 

X 

HC' X CH 

I I 

HC X y CX 

x cr 

H 

Formula II. 

Finally, there is a third kind of relation, which is that between 
hydrogens (1) and (4), (2) and (5), and (3) and (6) ; and, by 
replacing such a pair, we should get a compound represented 
by the general formula „ 

HC X X CH 

I i 

HC X .CH 

x cr 
x 

Formula HE. 



BENZENE. 241 

The hypothesis suggests no other possibilities. We see thus 
that the hypothesis indicates the existence of three, and only 
three, classes of di-substitution products of benzene. There 
ought to be three, and only three, di-chlor-benzenes ; three, 
and only three, di-brom-benzenes, etc. 

The di-substitution products have been studied very exhaust- 
ively for the purpose of determining definitely whether the 
conclusion above reached is in accordance with the facts ; and 
it may be said at once, that every fact thus far discovered is in 
harmony with the hypothesis. Three well-marked classes of 
isomeric di-substitution products of benzene are known, and 
only three ; and many representatives of th*e three classes have 
been studied carefully. There are many other facts of less 
importance known which furnish arguments in favor of the ben- 
zene hypothesis expressed in the formula above discussed, but 
this is not the place to discuss them. Let it suffice, for the 
present, to recognize that the hypothesis is in accordance with 
the most important facts known to us. 

There is one point which has not been touched upon, and 
that is the relation of the carbon atoms to each other. In 
regard to this, as well as to the relation between the carbon 
atoms in etlrylene and acetylene, we know nothing. The 
formula is commonly written thus : — 

H 

HC^ X CH 

I II 

HCU /CH 

H 

which indicates that the carbon atoms are joined together 
alternately by single and by double bonds. This formula, 
however, expresses something about which we know nothing, 
and concerning which it is difficult, at present, to form any 
conception. The simple formula 



242 BENZENE SERIES OF HYDROCARBONS. 

H 

HC X X CH 

I I 

HC X /CH 

H 

leaves the question as to the relation between the carbon atoms 
entirely open, as it is in fact. 

The benzene hypothesis has thus been treated somewhat fully 
for the reasons, that it has played an extremely important part 
in the study of the benzene derivatives, that its use serves 
greatly to simplify the study of these derivatives, and that in 
most text-books, whether elementary or advanced, the hypothesis 
is merely stated, while the student is left to find out for himself 
its meaning, and this he generally fails to do. We may now 
return to a stud}' of the facts upon which the hypothesis is 
founded. 



Toluene, C 7 H 8 (= C 6 H 5 .CH 3 ). — Toluene was known before 
it was obtained from coal tar, as it is formed by the dry distilla- 
tion of Tolu balsam, whence its name. Its relation to benzene 
is shown by its synthesis from brom-benzene and methyl 
iodide : — 

C 6 H 5 Br + CH 3 I + Na 2 = C 6 H 5 .CH 3 + NaBr + Nal. 

Note for Student. — Compare this reaction with that used in the 
synthesis of ethane from methane, of propane from ethane and 
methane, etc. 

According to this synthesis, toluene appears as methyl-benzene, 
or benzene in which one hydrogen is replaced by methyl ; or as 
phenyl-methane, or methane in which one hydrogen atom is re- 
placed by the radical phenyl, C 6 H 5 , which bears the same 
relation to benzene that methyl bears to marsh gas. 



XYLENES. 243 

Toluene is a colorless liquid which boils at 110° ; has the 
specific gravity 0.8824 at 0° ; and has a pleasant aromatic 
odor. 

It is very susceptible to the action of reagents yielding a large 
number of substitution-products, some of the most important 
of which will be taken up farther on. 

But one toluene or methyl-benzene has ever been discovered. 

Towards oxidizing agents its conduct is peculiar and interest- 
ing. The methyl is oxidized, while the phenyl remains intact. 
The product is a well-known acid, benzoic acid, which, as we 
have seen, breaks up readily into carbon dioxide and benzene. 
It has the composition C 7 H 6 2 , and is the carboxyl derivative 
of benzene, C 6 H 5 .C0 2 H. The oxidation of toluene is repre- 
sented by the equation 

C 6 H 5 .CH 3 + 30 = C 6 H 5 .C0 2 H + H 2 0. 

Xylenes, O 8 H 10 [= C 6 H 4 (CH 3 ) 2 ]. — That portion of light oil 
which boils at about 140° was originally called xylene. It 
was afterwards found that this coal-tar xylene consists of 
three isomeric hydrocarbons. As the boiling-points of these 
three substances lie quite near together, it is impossible to 
separate them by means of fractional distillation. By treat- 
ment with sulphuric acid, however, they can be separated, 
and thus obtained in pure condition. They are known as 
ortho -xylene, meta-xylene, and para-xylene. 

Ortho-xylene resembles benzene and toluene in its general 
properties, but boils at 140° to 141°. 

Meta-xylene boils at 137°. 

Para-xylene boils at 136° to 137°. 

These hydrocarbons have also been obtained from toluene by 



244 BENZENE SERIES OF HYDROCARBONS. 

means of the reaction made use of for the purpose of converting 
benzene into toluene : — 

C 6 H 4 <^ H 3 + CH 3 I + 2Na = C 6 H 4 <^ 3 +NaBr + Nal. 
Br CH 3 

This shows that they are all methyl-toluenes. There are 
three mono-brom-toluenes, known as ortho-, meta-, and para- 
brom- toluene. For the preparation of ortho-xylene, ortho- 
brom-toluene is used ; meta-brom-toluene yields meta-xylene, 
and para-brom-toluene yields para-xylene. 

Ortho- and meta-xylene have also been obtained from certain 
acids, which bear to them the same relation that benzoic acid 
bears to benzene : — 

rCH 3 
CeH s < CH 3 = C 6 H 4 (CH 3 ) 2 + C0 2 . 
(.C0 2 H 

The reaction hy which meta-xylene is formed from mesitylenic 
acid is of special importance, as will be pointed out. 

By oxidation, the xylenes undergo changes like that which is 
illustrated in the formation of benzoic acid from toluene, and 
which consists in the transformation of methyl into carboxyl. 

CH 
The first change gives acids of the formula C 6 H 4 < 3 , one 

C0 2 H 

corresponding to each xylene. By further oxidation, these 
three monobasic acids are converted into dibasic acids of the 

CO H 

formula C 6 H 4< ro 2 H - Thus, we have the three reactions, all 

of the same kind : — 

(1) C 6 H 5 . CH 3 +30 = C 6 H 5 . C0 2 H + H 2 ; 

(2) C 6 H 4 < jj +30 = C 6 H 4 < ^ + H 2 ; 

and (3) C 3 H 4 < gj^ + 3 = C 6 H 4 < gjg + H 2 0. 



XYLENES. 245 

nil 

The three monobasic acids of the formula. C 6 H 4< C q 3 h are 

known as ortho-toluic, meta-toluic, and para-toluic acids re- 
spectively ; and the three dibasic acids obtained from them 
are known as orlJio-phthalic, meta-plithalic, and para-phthalic 
acids. Starting thus from the three brom- toluenes, we get, 
first, three xylenes, then three toluic acids, and finally three 
phthalic acids. In each case, we distinguish between the 
three isomeric compounds by the prefixes ortJio, meta, and 
para. In a similar way, all di-snbstitution products of ben- 
zene are designated. We therefore have three series into 
which all di-substitution products of benzene can be arranged ; 
and these are known as the Ortho-series, the Meta-series, and 
the Para-series. In arranging them in this way, we may 
select any prominent di-substitution product, and call it an 
ortho compound; and then call one of its isomerides a meta 
compound, and the other a para compound. Having thus a 
representative of each of the three classes, the remainder of 
the problem consists in determining for each di-substitution 
product, by means of appropriate reactions, into which one 
of the three representatives it can be transformed. If from 
a given compound we get the representative of the ortho 
series, we conclude that the compound belongs to the ortho 
series ; if we get the representative of the meta series, we 
conclude that the compound is a meta compound ; and if we 
get the representative of the para series, we conclude that 
the compound is a para compound. As representatives, we 
may select either the three xylenes or the three phthalic 
acids. "Now, to repeat, am r di-substitution product of ben- 
zene which can be converted into ortho-xylene or into ortho- 
phthalic acid is regarded as an ortho compound, etc. 

This classification of the di-substitution products of benzene 
into 'the ortho, meta, and para series, by means of chemical 
transformations, is entirely independent of an} T hypothesis re- 



246 BENZENE SERIES OT HYDROCARBONS. 

garding the nature of benzene. We may now ask, however, 
which one of the three general expressions given above (see 
formulas I., II., and III., p. 240) represents the relation of the 
groups in the ortho compounds, which one the relation in the 
meta compounds, and which one the relation in the para com- 
pounds. If we can answer these questions for any three 
isomeric di-substitution products, the answer for the rest will 
follow. To reduce the problem to simple terms, therefore, 
let us take the three xylenes. We have three xylenes and 
three formulas : how can we determine which particular form- 
ula to assign to each xylene ? 

As may be imagined, this determination is by no means a 
simple matter ; and it has been the occasion of a great mam 7 
investigations. Theoretically, the simplest method available 
consists in carefully studying the substitution-products of each 
xylene, to discover how many varieties of mono-substitution 
products can be obtained from each. The formulas are : — 

CH3 ^U-3 ^H-3 

(4)HC 7 X C.CH 3 (4)HC X X CH(1) (4)HC / X CH(1) 

I I II I ( 

(3)HC X /CH(1) (3)HC X /CCH 3 (3)HC X /CH(2) 

C C C 

(2) (2) OH * 

Formula I. Formula II. Formula TTT . 

Each of the four unreplaced benzene hydrogens of the xylene 
of formula III. bears the same relation to the molecule. It 
therefore should make no difference which one is replaced, the 
product ought to be the same. This should not be true of 
the xylenes represented by formulas I. and II. That xylene, 
whose structure is represented by formula III. , ought therefore 
to yield but one kind of mono-substitution product. On studj- 
ing the xylenes, we find the one which boils at 136° to 137°, 



ETHYL-BENZENE. 247 

called para-xylene, yields but one kind of mono-substitution 
products ; that is, we can get from it only one mono-brom- 
xylene ; only one mono-nitro-xylene, etc. We therefore con- 
clude that para-xylene is represented by formula III. above ; 
and, further, that formula III., on p. 240, is the general ex- 
pression for all para compounds. 

Examining formula I., on the preceding page, in the same 
way, we see that H(l) and H(4) bear the same relation to the 
molecule ; and that H(3) and H(2) also bear the same relation 
to the -molecule, though different from that of H(l) and H(4). 
Two chlor-xylenes of the formulas 



CH 3 




CH 3 


.C. 




.C. 


HC X X CCH, 

1 1 


and 


HC X X C.CH 3 

1 1 


HC V /CC1 




HC X /CH 

x cr 



H CI 

ought to be obtainable from the xylene of formula I. 

In the same way three mono-substitution products might be 
obtainable from the xylene of formula II. The method, the 
principle of which is thus indicated briefly, while theoretically 
simple enough, is ver} 7 difficult in its application, except in the 
case of the para compounds. Other methods have therefore 
been used, and these will be discussed under mesitylene and 
naphthalene. It may be said, in anticipation, that the result 
of all observations point to formula I. for ortho-xylene ; to 
formula II. for meta-xylene, and to formula III. for para- 
xylene. 

Ethyl-benzene, C 8 H 10 (= C fi H 5 .C 2 H 5 ). — This hydrocarbon is 
isomeric with the xylenes, but differs from them in that it con- 
tains an ethyl group in the place of one hydrogen of benzene, 



248 BENZENE SERIES OE HYDROCARBONS. 

instead of two methyl groups in the place of two hydrogens of 
benzene. 

It is made by treating a mixture of brom-benzene and ethyl 
bromide with sodium : — 

C 6 H 5 Br + C 2 H 5 Br + 2 Na = C 6 H 5 .C 2 H 5 + 2 NaBr. 

Its conduct towards oxidizing agents distinguishes it from the 
xylenes. It yields benzoic acid, just as toluene does. In this 
case, as in that of toluene, the paraffin radical is converted into 
carboxyl. It has been found that no matter what this radical 
may be, it is, under the same circumstances, converted into car- 
boxyl. Thus, the conversions indicated below take place : — 



CeH 5 .CH 3 


gives 


C 6 H 5 .C0 2 H. 


C6H 5 .C 2 H 5 


u 


C 6 H 5 .C0 2 H. 


C 6 H 5 .C 3 H 7 


u 


CeH 5 .C0 2 H. 


C 6 H 5 .C 5 H n 


a 


GgHg .C0 2 H. 


< «<S 


a 


pu / C0 2 H 
C6H4< C0 2 H 


^ 3 ±1 7 


a 


C 6 H 4 < 2 , etc., etc. 

l^U 2 ti 



Mesitylene, C 9 H 12 [=C 6 H 3 (CH3)3]. — Mesitylene is contained 
in small quantity in light oil, and can be obtained in pure con- 
dition from this source. It is most readily prepared by treating 
acetone with sulphuric acid : — 

3 C 3 H 6 = C 9 H U + 3 H 2 0. 

It is a liquid resembling the lower members of the series in its 
general properties. It boils at 163°. 

Its conduct towards oxidizing agents shows that it is a tri- 
methyl-benzene. When boiled with dilute nitric acid, it yields 
mesitylenic acid, C 9 H 10 O 2 , and uvitic acid, CgHgO^ ; and, by 



MESITYLENE. 



249 



further oxidation with chromic acid, trimesitic acid, C9H 6 6 , is 
formed. By distillation with lime, mesitylenic acid yields meta- 
xylene and carbon dioxide ; uvitic acid yields toluene and car- 
bon dioxide ; and trimesitic acid yields benzene and carbon 
dioxide. The formation and decomposition of the acids may 
be represented by the equations following : — 



C 6 H 3 (CH 3 ) 3 +30 

Hesitylene. 

(CH 3 
C 6 H 3 j CH 3 +30 

Mesitylenic acid. 

(CH 3 
C 6 H 3 j C0 2 H +30 
V-C0 2 H 

Uvitic acid. 

rCH 3 
CeH 3 -j CH 3 
((X) 2 H 

Mesitylenic acid 

(CH 3 
C 6 hJC0 2 H 
(.C0 2 H 

Uvitic acid. 

rC0 2 H 

C 6 H 3 ] C0 2 H 

(_C0 2 H 

Trimesitic acid. 



rCH 3 
C 6 H 3 < CH 3 + H 2 ; 
(C0 2 H 

Mesitylenic acid. 

(CH 3 
C 6 hJC0 2 H + H 2 0; 
(C0 2 H 

Uvitic acid. 

( C0 2 H 
C 6 H 3 ]C0 2 H + H 2 0; 
(C0 2 H 

Trimesitic acid. 



C 6 H 4 



{Z: +co °-> 



Meta-xylene. 

C 6 H 5 .CH 3 + 2C0 2 ; 

Toluene. 



C 6 H 6 + 3 C0 2 . 

Benzene. 



These transformations show clearly tha.t mesitylene is tri- 
methyl-benzene, but they do not show in what relation the 
methyl groups stand to each other. 

An ingenious speculation in regard to this relation is based 
upon the fact that mesitylene is formed from acetone. It 



250 BENZENE SERIES OF HYDROCARBONS. 

appears probable that each of the three molecules of acetone 
taking part in the reaction, 

3 C 3 H 6 = CgH^ + 3 H 2 ? 

undergoes the same change. As the product contains three 
methyl groups, the simplest assumption that can be made is 
that each acetone molecule gives up water as represented 
thus : — 

CH3-CO-CH3 = CH3-C-CH + H 2 0. 

Acetone. 

We thus have three residues, CH 3 -C-CH, and these unite 
to form trimethyl benzene. The only way in which the union 
can be represented, assuming that all three act in the same 
way, is this : — 

CH 3 
HCT X CH 

I I 

xlgC-.C/x /U.OH3 

H 

According to this reasoning, mesitylene is a symmetrical com- 
pound, — that is to say, each of the three methyl groups bears 
the same 'relation to the molecule ; and the same is true of each 
of the three benzene-hydrogen atoms. 

This view has been tested by replacing the three hydrogen 
atoms successively by bromine ; and it has been found that 
the view is confirmed, as but one mono-bromine substitution- 
product of mesitylene has ever been obtained. Accepting the 
formula above given for mesitylene, an important conclusion 
follows regarding the nature of meta-xylene. For we have 
seen that, by oxidizing mesitylene, we get, as the first product, 
mesitylenic acid, — which is mesitylene, one of whose methyls 
has been converted into carboxyl. As all the methyl groups 



PSEUDOCUMENE. 251 

bear the same relation to the molecule, it makes no difference 
which one is oxidized. The acid has the formula 



CH 3 


HC X X CH 

i i 


1 1 

x cr 


H 



Now, by distilling this acid with lime, carbon dioxide is given 
off, and meta-x^dene is produced. 

As the change consists in removing the carboxyl, and replac- 
ing it by hydrogen, it follows that meta-xylene must be repre- 
sented by the formula 

CH 3 

HC X X CH 

I I 

HC\ /C.CH3 

X (T 
H 

and consequently that, in all meta compounds, the two substi- 
tuting atoms or groups bear to each other the relation which the 
two methyl groups bear to each other in this formula for meta- 
xylene. 

N. 

Pseudocumene, C 9 Hi 2 |> C 6 H 3 (CH 3 )3]. — This hydrocarbon, 
which is isomeric with mesitylene, occurs in coal-tar oil, from 
which it can be made in pure condition. Its properties are 
similar to those of the lower members of the series. It boils 
at 169.8°. 

Pseudocumene has been made synthetically from brom-para- 
xylene and methyl iodide, and also from brom-meta-xylene and 



252 



BENZENE SERIES OF HYDROCARBONS. 



methyl iodide. How this is possible, will be understood by an 
examination of the formulas below : — 

CH 3 CH 3 

HC X X CH UC / X CH 

II II 

H(\ y CBr HC\ /C.CH 3 

cr x c 

Brom-para-xylene. Brom-meta-xylene. 

Replacing the bromine by methyl, in either of the compounds 
represented, the product would have the formula 

CH 3 

HC X X CH 

I I 

HC- s. / \u . (_/ JJ.3 

X C X 

CH 3 

which is that of pseudocumene. 

Cymene ' X C 10 H 14 f C 6 H 4 < CH3 ^ . 

Para-methyl-isopropyl-benzene, J V C 3 H 7 / 

This hydrocarbon is of special importance and interest, on 
account of its close connection with two well-known groups 
of natural substances, — the groups of which camphor and oil 
of turpentine are the best-known representatives. It occurs in 
the oil of caraway and the oil of thyme. The terpen es, which 
are hydrocarbons of the formula C 10 H 16 , and of which oil of 
turpentine is the best known, easily give up two hydrogen 
atoms and }deld cymene. Probably the simplest way to pre- 
pare cymene is to treat camphor with phosphorus pentasul- 
phide, zinc chloride, or phosphorus pentoxide. 
It is a liquid of a pleasant odor. It boils at 175°. 



CYMENE. 253 

It has been made synthetically from para-brom-toluene and 
isopropyl bromide : — 

C 6 H 4 <^ H3 +C 3 H 7 Br + 2Na 
Br 

= C 6 H 4 <^ 3 + 2NaBr, 

which clearly shows its relation to benzene. As the final 
product of its oxidation, it yields para-phthalic (terephthalic) 
acid : — 

see p. 248. 



CHAPTER XV. 

DERIVATIVES OP THE HYDROCARBONS, CnH^e, 
OF THE BENZENE SERIES. 

Recalling what we learned under the head of Derivatives of 
the Paraffins, we naturally look for representatives of all the 
classes of compounds there met with. The derivatives of the 
paraffins were classified into : — 

1. Halogen derivatives. 

2. Ox}'gen derivatives, including the Alcohols, Aldelrydes, 

Acids, etc. 

3. Sulphur derivatives, including the Mercaptans, Sulphonic 

Acids, etc. 

4. Nitrogen derivatives, including Cyanides, Amines, Nitro com- 

pounds, etc. 

5. Metallic derivatives. 

The derivatives of the benzene hydrocarbons may be classi- 
fied in the same way, but a change in the order of consideration 
will be somewhat more convenient iu this connection, owing to 
many points of analogy which exist between the halogen sub- 
stitution-products, the nitro compounds, and the sulphonic 
acids. All of these three classes of derivatives of the benzene 
hydrocarbons are made by direct treatment of the hydrocarbons 
with the substituting agents, and in some respects resemble 
each other, so that they will be studied in connection. As 
the araido derivatives of this series are made almost exclusively 
from the nitro compounds by reduction, they will be taken up 
in connection with the nitro compounds ; and, further, by treat- 
ment of the amido compounds with nitrous acid, a new class 






Halogen derivatives of benzene. 255 

of nitrogen derivatives, known as diazo compounds, not met 
with in connection with the paraffins, is formed. These will 
be taken np after the amido compounds. 

After these classes have been studied, we shall take up in 
turn the oxygen derivatives, which include the phenols or simple 
hydroxyl derivatives of the hydrocarbons, the alcohols, alde- 
hydes, acids, and ketones ; and, finally, the hydroxy -acids, 
which are strictly analogous to the hydroxy-acids of the paraffin 
series. 

We have thus the following classes : — 

1. Halogen derivatives. 5. Sulplwnic acids. 9. Acids. 

2. Nitro compounds. 6. Phenols. 10. Ketones (and 

3. Amido compounds. 7. Alcohols. Quinones). 

4. Diazo compounds. 8. Aldehydes. 11. Hydroxy-acids. 

The relations of most of these classes to the hydrocarbons 
are the same as those of the corresponding derivatives of the 
paraffin series to the paraffins ; and the general methods of 
preparation, as well as the reactions, are the same. Hence, 
most of the knowledge acquired in the first part of the course 
may be applied to the series now under consideration. 

An enormous number of derivatives of the benzene hydrocar- 
bons have been prepared and studied ; but we need study only 
very few in order to acquire a general knowledge of them. In 
the following a few of the more important representatives of 
each class will be studied, mainly with the object of illustrating 
general facts and general relations. 

Halogen Derivatives op Benzene. 

Very little need be said in regard to these derivatives. By 
direct action of bromine or chlorine upon benzene the hydrogen 
atoms are replaced one after another, until, as the final products, 
hexa-chlor -benzene , C 6 C1 G . and hexa-brom-benzene, C 6 Br G , are ob- 
tained. It has already been stated that, when the action takes 



256 DERIVATIVES OF THE BENZENE SERIES. 

place in direct sunlight, addition-products, C 6 H 6 C1 6 and C 6 H 6 Br 6 , 
are formed. Benzene hexachloricle, C 6 H 6 C1 6 , is formed also 
when chlorine is conducted into boiling benzene. The addition- 
products are readily decomposed, yielding tri-substitution prod- 
ucts of benzene and halogen acid : — 

C 6 H 6 Br 6 = C 6 H 3 Br 3 + 3 HBr. 

The substitution-products are very stable. They are, as a 
rule, formed more easily than the halogen derivatives of the 
paraffins, and, as a rule, they do not give up the halogens as 
readily. Thus, while it is possible. in the paraffin derivatives 
to replace chlorine and bromine by hydroxyl, the amido group, 
etc., these replacements cannot easily be effected in the benzene 
derivatives. The halogens can be removed by sodium, as 
shown in the synthesis of hydrocarbons : — 

C 6 H 5 Br + CH 3 I + 2 Na 
= C 6 H 5 .CH 3 + NaBr -f Nal, etc., etc. 

They can also be removed by nascent hydrogen, the Irydro- 
carbons being regenerated : — 

C6H 4 C1 2 + 4H = C 6 H 6 + 2 HC1. 

This kind of reverse substitution is not, however, effected 
easily. 

Perhaps the best known of the di-substitution products of the 
class under consideration is 

Dibrom-benzene, CeHiBiv,, which is one of the products of 
the direct treatment of benzene with bromine. This being a 
di-substitution product of benzene, it follows, from what has 
been said in regard to isomerism in this group, that three 
isomeric varieties of the substance ought to be obtainable ; and 
the interesting question suggests itself : which one of the 
three possible dibrom-benzenes is formed by direct treatment of 
benzene with bromine ? The answer to the question is equally 



HALOGEN DERIVATIVES OF TOLUENE. 257 

interesting. The main product of the action is para-dibrom* 
benzene, while there is always formed in much smaller quantity 
some of the ortlio product. The reason why these products 
are obtained, and not the meta compound, is unknown ; nor 
has any plausible hypothesis been suggested to account for the 
fact. 

In studjing the substitution-products of benzene, one of the 
first problems which present themselves is the determination 
of the relations which the substituting atoms or groups bear 
to each other. The determination is made, as has been 
stated, by transforming the compounds into others, the rela- 
tions of whose groups are known. Thus, to illustrate, when 
benzene is treated under the proper conditions with bromine, 
two dibrom-benzenes are formed. Without investigation, we, 
of course, cannot tell to which series these compounds belong. 
But, by treating that product which is formed in larger quantity 
with methyl iodide and sodium, we get para-xylene. In other 
words, by replacing the two bromine atoms of the dibrom- 
benzene by methyl groups, we get a compound which we know 
belongs to the para series ; and, therefore, we have determined 
that the bromine product is a para compound. In the follow- 
ing the chief reactions made use of for effecting the trans- 
formations of the derivatives will be discussed. . 

Halogen Derivatives of Toluene. 

As toluene is made up of a residue of marsh gas, methyl, 
CH 3 , and a residue of benzene, phenyl, C 6 H 5 , we may naturally 
expect to find that it yields two classes of substitution-products : 
viz., (1) Those in which the substituting atom or group replaces 
one or more hydrogen atoms of the phenyl group; and (2) those 
in which the substitution takes place in the methyl. In gen- 
eral, when treated with chlorine or bromine in direct sunlight, 
or if boiling, toluene yields products of the second class ; while, 
when treated in the dark, or if cold, it yields products of the 



258 DEBIT ATIYES OF THE BENZENE SEBIES. 

first class. Thus, we have the two parallel series of chlo- 
rine derivatives : — 

i. ii. 

CeEltCl •CH 3 CgH 5 .CH 2 C1. 

C/gil3^l2 •O-H.3. CgH^ .CHC1 2 . 

CgH 2 Cl 3 . CH 3 . C 6 H 5 .CC1 3 . 

When a member of the first class is oxidized, the methyl is 
changed, and the rest of the compound remains unchanged, 
as in the case of toluene. Thus, the first substance of class I. 
yields the product C 6 H 4 C1.C0 2 H; the second, C 6 H 3 C1 2 .C0 2 H, 
etc. These products are substituted benzoic acids. On the 
other hand, all the members of the second class yield the same 
product that toluene does; viz., benzoic acid. Hence, by 
treatment with oxidizing agents, it is easy to distinguish between 
the members of the two classes. Further, the halogen atoms 
contained in the methyl are not as firmly held in combination 
as those in the phenyl. When, for example, the compound 
C G H 5 .CHC1 2 , which is called benzol chloride, is treated with 
water, both chlorine atoms are replaced by oxygen, the product 
being the aldehyde C 6 H 5 .CHO, which, as we shall see, is the 
familiar substance, oil of bitter almonds. When, however, the 
isomeric di-chlor-toluene C 6 H 3 C1 2 .CH 3 is heated with water, no 
change takes place. 

Eegarding those simple substitution-products of toluene which 
contain one halogen atom in the phenyl, such as mono-brom- 
toluene, CeH^Br.CHg, we see that they are di-substitution prod- 
ucts of benzene, and hence capable of existing in three isomeric 
varieties, ortho, meta, and para. The products formed by 
direct treatment of toluene with chlorine or bromine are mixtures 
consisting mostly of the para compound, together with a much 
smaller quantity of the ortho compound. 

The determination of the series to which one of these products 
belongs can be made by replacing the halogen by methyl, and 



NrTRO COMPOUNDS OF BENZENE AND TOLUENE. 259 

thus getting the corresponding xylene. The main product of 
the action of bromine on toluene is thus converted into para- 
xylene, and is therefore para-brom- toluene. 

Halogen Dekivatives of the Higher Members of 
the Benzene Series. 

Concerning the halogen derivatives of xylene, it need only be 
said that the only one of the three xylenes from which pure 
products can easily be obtained is para-xylene. When this is 
treated with bromine it yields but one mono-brom-xylene. The 
significance of this fact has been discussed above. The mono- 
substitution products obtained from the other xylenes are 
mixtures which it is very difficult, and in some cases impos- 
sible, to separate into tteir constituents. Mesitylene and 
pseudocumene, though both are tri-methyl-benzenes, conduct 
themselves quite differently towards bromine, — the former yield- 
ing only one mono-bromine product ; the latter, a mixture of 
several. 

Nitro Compounds of Benzene and Toluene. 

In speaking of nitro compounds in connection with the paraf- 
fin derivatives (see p. 100), it was stated that they are obtained 
much more readily from the benzene hydrocarbons than from 
the paraffins. But few nitro derivatives of the paraffins are 
known. As will be remembered, they cannot be prepared by 
treating the paraffins with nitric acid, but must be made by 
circuitous reactions, the principal one being the treatment of 
the halogen derivatives with silver nitrite : — 

C 2 H 5 Br + AgN0 2 = C 2 H 5 (N0 2 ) + AgBr. 

Nitro -ethane. 

The preparation of a nitro derivative of a hydrocarbon of 
the benzene series is a simple matter. It is only necessary to 
bring the hydrocarbon in contact with strong nitric acid, when 
reaction takes place, and one or more hydrogen atoms of the 



260 DERIVATIVES OF THE BENZENE SERIES. 

hydrocarbon are replaced by the nitro group N0 2 , as represented 
in the equations, — 

C 6 H 6 + HN0 3 = C 6 H 5 . N0 2 + H 2 ; 

C 6 H 5 . N0 2 + HNO3 = C 6 H,(N0 2 ) 2 + H 2 ; 

C 6 H 5 .CH 3 + HN0 8 = C 6 H 4 < ^° 2 + H 2 ; 

Cti 3 

C 6 H 4 < ^ 2 + HN0 3 = C 6 H 3 < £??»>* 4- H 2 0. 

UM 3 Ct± 3 

The nitro compounds thus obtained are not acids, nor are 
they ethereal salts of nitrous acid, as the formulas might lead 
us to suppose. The most rational view is, that they are 
formed from nitric acid by the substitution of radicals for 
hydroxyl, as indicated thus : — 

CeHsJH+'HOJ.NO, = C 6 H 5 .N0 2 + H 2 0. 

Mono-nitro-benzene, C 6 H 3 .N0 2 . — This substance is made 
by treating benzene with concentrated nitric acid, or with a 
mixture of ordinary concentrated nitric and sulphuric acids. 
In the latter case, the sulphuric acid facilitates the reaction, 
probably by preventing the dilution of the nitric acid by the 
water necessarily formed. 

Experiment 58. Make a mixture of 150 cc ordinary concentrated 
sulphuric acid, and 75 cc ordinary concentrated nitric acid. Let it cool 
to the ordinary temperature. Put the vessel containing it in water, 
and add about 15 cc to 20 cc benzene, a few drops at a time, waiting each 
time until the reaction is complete. Shake well until the benzene is 
dissolved; then pour slowly into about a litre of cold water. A yellow 
oil will sink to the bottom. This is nitro-benzene. Pour off the acid 
and water ; wash two or three times with water ; separate the water 
by means of a pipette, and dry by adding a little granulated calcium 
chloride. After standing for some time, pour off from the calcium 
chloride, and distil from a proper sized distilling-bulb, noting the 
boiling temperature. 

Nitro-benzene is a liquid which boils at 205°, and has the 



MTBO-TOLUENES. 261 

specific gravity 1.2. Its odor is like that of the oil of bitter 
almonds, and it is hence used in many cases instead of the 
latter. It is known as the essence of mirbane. It is manufac- 
tured on the large scale, and used principally in the preparation 
of aniline. 

Dinitro-benzene, C H 4 (NO 2 ) 2 . • — This is a product of the 
further action of nitric acid on benzene, or on nitro-benzene. 

Experiment 59. Make a mixture of 50 ec concentrated sulphuric 
acid, and 50 cc fuming uitric acid. Without cooling add very slowly 
about 10 cc benzeue from a pipette with a fine opening. After the 
action is over, boil the mixture for a short time ; then pour into about 
half a litre of water. Filter off the solid substance thus precipitated, 
press it between layers of filter-paper, and crystallize from alcohol. 

Dinitro-benzene crystallizes in long, fine needles, or thin, 
rhombic plates. Melting-point, 91°. 

By means of two reactions, which will be described under 
the head of Diazo Compounds, it is a simple matter to replace 
the two nitro groups by bromine, thus converting dinitro-ben- 
zene into dibrom-benzene. When the latter is -converted into 
xylene, the product is meta-xylene. Hence, ordinary dinitro- 
benzene is a meta compound. 

Nitro-toluenes, CgH^NCXj.CHo. — When toluene is treated 
with strong nitric acid, substitution always takes place in the 
phenyl. The chief mono-nitro-toluene is a para compound ; 
while, at the same time, a little of the isomeric ortho compound 
is obtained. 

Note for Student. — What mono-bromine products are formed 
by direct treatment of toluene with bromine ? Given a mono-nitro- 
toluene, how is it possible to determine whether it belongs to the 
ortho, the meta, or the para series? 

By treatment with nascent hydrogen, the nitro-toluenes are 
converted into the corresponding amido compounds, called 
Toluidines (which see) . 



262 DERIVATIVES OF THE BENZENE SEMES. 

Amido Compounds of Benzene, etc. 

The amido derivatives of the paraffins are made, for the most 
part, by treating the halogen derivatives with ammonia : — 

C 2 H 5 Br + NH 3 = C 2 H 5 .NH 2 + HBr. 

In speaking of these derivatives, however, attention was called 
to the fact that they can also be made by treating nitro com- 
pounds with nascent hydrogen. The latter method is one of 
great importance in the benzene series. It is used exclusively 
in the preparation of the amido derivatives of the benzene 
hydrocarbons. Several of these derivatives are well known, 
the simplest and best known being amido -benzene or aniline. 

Aniline, C 6 H 7 N(= C 6 H 5 .NH 2 ). — Aniline was first obtained 
from indigo by distillation. Anil is the Portuguese and French 
name of the indigo plant, and it is from this that the name 
aniline is derived. Aniline is found in coal tar and in bone oil, 
a product of the distillation of bones. It is prepared b}' re- 
duction of nitro-benzene with nascent hydrogen. On the large 
scale the hydrogen is obtained from hydrochloric acid and iron. 
For laboratory purposes tin and hydrochloric acid are perhaps 
best. Other reducing agents, such as an ammoniacal solution 
of ammonium sulphide, hydriodic acid, etc., also effect the 
change, which is represented by the following equation: — 

C 6 H 5 . N0 2 + -6 H = C 6 H 5 . NH 2 + 2 H 2 0. 

Experiment 60. Arrange a litre flask with a stopper and a straight 
glass tube from two to three feet long. Put in the flask 85& granu- 
lated tin and about 400" ordinary concentrated hydrochloric acid. Now 
add slowly 50s nitro-benzene. After the action is over, add enough 
water to dissolve the contents of the flask, then add sodium hydroxide 
until the precipitate first formed is nearly all dissolved. Distil, when 
aniline and water will pass over. Separate as in the case of brom- 
ethane (see p. 30). 

Aniline is a colorless liquid which rapidly becomes colored in 



TOLUIDINES. 263 

the air. It boils at 184.5°. It solidifies at a low temperature ; 
is easily soluble in alcohol, but slightly soluble in water. The 
solution in water has only a very slight alkaline reaction. 

Experiment 61. To an aqueous solution of a little of the aniline 
obtained in Exp. 60, in a test-tube, add a filtered solution of bleach- 
ing powder (calcium hypochlorite). A beautiful purple color is pro- 
duced. 

To a solution of aniline in concentrated sulphuric acid add a few 
4-ops of an aqueous solution of potassium bichromate. A blue color 
is produced. 

Aniline bears to benzene the same relation that cthyl-amine 
or amido-ethane bears to ethane. It is a substituted ammonia, 
and, like other bodies of the same class, it unites directly with 
acids, forming salts. Thus, with hydrochloric, nitric, and 
sulphuric acids the action takes place as represented below : — 

C 6 H 5 . NH 2 + HC1 = (C 6 H 5 . NH 3 ) CI ; 
C 6 H 5 .NH 2 + HN0 3 = (C 6 H 5 .NH 3 )N0 3 ; 
C 6 H 5 . NH 2 + H 2 S0 4 = C 6 H 5 . NH 3 HS0 4 . 

The decomposition of aniline hydrochloride by means of 
a caustic alkali takes place as represented in the following 
equation : — 

C 6 H 5 .NH 3 C1 + KOH = C 6 H 5 .NH 2 + H 2 + KC1. 

Among the most interesting changes which can be effected in 
aniline is that which takes place when it is treated with nitrous 
acid (see Diazo Compounds, below) . 

Note for Student. — What change is usually effected in amiclo 
compounds by treating them with nitrous acid? 

Toluidines, amido-toluenes, C G H 4 < SS" 2 . — The tolui- 

CH3 
dines, of which there are three corresponding to the three nitro- 

toluenes, are made from the latter in the same way that aniline 

is made from nitro-benzene. As para-nitro-toluerie is the best 



264 DERIVATIVES OE THE BENZENE SERIES. 

known of the three nitro-toluenes, so para-toluidine is the best 
known of the three toluidines. 

The properties of the toluidines are much like those of aniliue. 

Treated with various oxidizing agents, a mixture of aniline 
and the toluidines is converted into a compound known as 
rosaniline. This is the mother substance of the large group of 
compounds known as the aniline dyes. Rosaniline and its de- 
vivatives, the aniline dyes, will be treated under Tn-phenyl- 
methane (which see) . 

By nitrous acid the toluidines are transformed in the same 
way that aniline is (see Diazo Compounds). 

The xylidines bear to the three xylenes the same relation 
that aniline bears to benzene. It is not a simple matter to get 
any one of them in pure condition. 

Diazo Compounds of Benzene, etc. 

The usual action of nitrous acid on amido compounds is 
represented by the equation, — 

R.NH 2 + HN0 2 = R.OH + H 2 + N 2 . 

When an amido derivative of a hydrocarbon of the benzene 
series is treated with nitrous acid, and certain precautions are 
taken, a product is obtained which contains two nitrogen 
atoms, and which is, therefore, called a diazo compound. 
Thus, in the case of aniline sulphate, the action is represented 
by the equation, — 

C 6 H 5 NH 2 .H 2 S0 4 -f HN0 2 = C 6 H 5 N 2 .HS0 4 + 2H 2 0. 

Aniline sulphate. Diazo-benzene sulphate. 

So, also, with the nitrate we have, — 

C 6 H 5 NH 2 .HN0 3 + HN0 2 = C 6 H. 5 N 2 .N0 3 + 2 H 2 0. 

Aniline nitrate. Diazo-benzene nitrate. 

From these salts the diazo-benzene itself can be set free by 
means of acetic acid. It has been found to have the formula 



DIAZO COMPOUNDS OF BENZENE, ETC. 



265 



C G H 5 N 2 (OH). This compound is, however, very unstable, and 
is at once decomposed. 

Experiment 62. Arrange an apparatus as shown in Fig. 14. In 
flask A put arsenic trioxide (about 50s), and through the funnel-tube 
pour 40 cc to 50 cc ordinary nitric acid (sp. gr. 1.35). B is an empty 
cylinder surrounded by water. In place of the two small flasks repre- 
sented in the figure one test-tube of about 50 cc capacity may be used, 
and in it should be brought 10s aniline nitrate, and 12 cc ice-cold water. 




Fig. 14. 



This is placed in ice water. Pass a current of the oxides of nitrogen 
until the material in the tube dissolves. Add to the solution about 
an equal volume of alcohol previously cooled to 0°, and then a little 
cold ether. If the operation has been successful, a copious precipitate 
of crystals of diazo-benzene nitrate will appear. Filter off with the 
aid of a suction-pump, and, without delay, proceed to study the proper- 
ties of the compound. 

(a) Dissolve a little in water of the ordinary temperature, and allow 



266 DERIVATIVES OF THE BENZENE SERIES. 

the solution to stand. Decomposition, indicated by change of color, 
will take place. 

(5) Boil a little with water in a test-tube, and notice the odor of 
phenol or carbolic acid. 

(c) Boil a few grams with alcohol in a test-tube, and notice the ease 
with which the decomposition takes place. The chief product is ethyl- 
phenyl ether or phenetol, C 6 H 5 . O . C 2 H 3 . 

(d) Boil some with hydrochloric acid. Chlor-benzene is formed, 
which sinks to the bottom when water is added. 

In all these experiments a gas is evolved which can be shown to be 
nitrogen. Collect some, and show that it does not support combustion. 

(e) Place a very little of the compound, dried by pressing in filter- 
paper, on an anvil, and strike it sharply with a hammer. It explodes. 

The above experiments serve to indicate the instability of 
diazo-benzene nitrate. This same instability is characteristic 
of all diazo compounds, and it is the ease with which they 
undergo a variety of changes that makes them so valuable. 
The principal changes are : — 

1. That illustrated in Exp. 62 (b). which is brought about 
by boiling with water. The action is represented thus : — 

C 6 H 5 N 2 . N0 3 + H 2 = C 6 H 5 . OH 4- N 2 + HN0 3 . 

Phenol. 

2. That illustrated in Exp. 62 (c), which is effected by boil- 
ing with alcohol : — 

C 6 H 5 N 2 . N0 3 + C 2 H 5 . OH = C 6 H 5 . . C 2 H 5 + N 2 + HN0 3 . 

Phenetol. 

3. That effected by hydrochloric acid as illustrated in Exp. 
62 (d) : — 

C 6 H 5 N 2 .N0 3 + HC1 = C 6 H 5 C1 +..N, + HN0 3 . 

Hono-chlor-benzene. 

Changes similar to the last are effected by hydrobromic and 
hydriodic acids, the chief products being brom-benzene and 
iodo-benzene respectively. 

From the above it follows that, if we have a compound con- 
taining a nitro group, we can, by making the diazo compound, 



SULPHONIC ACIDS OF BENZENE, ETC. 267 

transform it (1) into the corresponding hydroxyl derivative; 
(2) into the corresponding chlorine, bromine, or iodine deriva- 
tive ; or, (3) we can make ethers containing such groups as 
C 2 H 5 0, CH 3 0, etc. These reactions involving the use of the 
diazo compounds have been used very extensively in the inves- 
tigation of the substitution-products of the benzene series. 

Note for Student. — How can the relation of the groups in cli- 
nitro-benzene be determined by using the cliazo reactions? 

As regards the relation of diazo-benzene to benzene, it seems 
clear, from the reactions above considered, that in it the phenyl 
group C 6 H 5 is present, and that this is in combination with two 
nitrogen atoms. In the compounds, the two atoms of nitrogen 
form the connecting link between the phenyl group and the 
other constituent, as expressed in the formulas 

C 6 H 5 -N 2 -N0 3 , 
C 6 H 5 -N 2 -OK, 
C 6 H 5 -N 2 -Br, etc. 

The decompositions all indicate the correctness of this view. 
How the nitrogen atoms are united, we do not know. 

Sulphonic Acids of Benzene, etc. 

The methods of preparation of the sulphonic acids, and the 
relations of these acids to the hydrocarbons, were discussed 
pretty fully, in connection with the paraffins. Three general 
methods for their preparation were given. These are : — 

1. Oxidation of the mercaptans ; thus, ethyl-sulphonic acid 
is formed by oxidation of ethyl-mercaptan, — 

C 2 H 5 .SH + 30 = C 2 H 5 .S0 3 H. 

2. Treatment of a halogen substitution-product with a sul- 
phite, — 

C 2 H 5 Br + Na 2 S0 3 = C 2 H 5 .S0 3 Na + NaBr. 



268 DEKIVATIVES OF THE BENZENE SERIES. 

3. Treatment of a hydrocarbon with sulphuric acid. This 
method is not applicable to the paraffins, but is the one used 
almost exclusively in the case of the benzene hydrocarbons. 
Benzene-sulphonic acid is formed thus : — 

C 6 H 6 + H 2 S0 4 = C 6 H 5 .S0 3 H + H 2 0. 

Toluene-sulphonic acid is formed thus : — 

C 6 H 5 .CH 3 + H 2 S0 4 = C 6 H 4 <^L + H 2 0. 

dU 3 h 

The reasons for regarding the sulphonic acids as sulphuric 
acid in which hydroxyl is replaced by radicals, were given on 
p. 76 ; and the student is advised carefully to re-read what 
is there said. 

Benzene-sulphonic acid, C 6 H 6 S0 3 (= ^ 6 fr 5 j S0 2 ]. — This 

acid is made by treating benzene with sulphuric acid. Simi- 
larly, and more easily, toluene-sulphonic acid, C 7 H 7 .S0 3 H, is 
made from toluene. 

Experiment 63. In a flask bring together about 50 cc toluene and 
100 cc concentrated sulphuric acid (ordinary). Heat on a water-bath 
and shake until most of the toluene is dissolved. Pour the contents 
of the flask into a large evaporating dish of at least 8 1 to 10 1 capacity, 
containing 4 1 to 5 1 water. Heat gently, and add gradually, stirring 
meanwhile, finely-powdered chalk, until the solution has become neu- 
tral. Pass through a muslin filter attached to a wooden frame, and 
wash thoroughly with hot water. Afterwards refilter the filtrate 
through a paper filter. Evaporate to quite a small volume (say 500 cc 
to 700 cc ), and filter from gypsum. In solution there is now the cal- 
cium salt of the sulphonic acid. Add just enough of a solution of 
sodium carbonate to precipitate exactly the calcium; filter off from 
the calcium carbonate, and evaporate to dryness, finally, on the water- 
bath. To prevent caking it is necessary to stir the thick, syrupy mass. 
When it is nearly dry, it is best to powder it, and complete the drying 
at 100° to 120° in an air-bath. The sodium salt can be used for a 
number of experiments. 



TOLtTEKE-SULPHOKIC ACID. 269 

Experiment 64. In a dry evaporating dish mix thoroughly 20s of 
sodium tolueue-sulphonate with 25s of phosphorus penta-chloride, by 
means of a dry pestle. The mass becomes semi-liquid and hot, and 
hydrochloric acid is given off, in consequence of the action of the 
moisture of the air on the chlorides of phosphorus. Hence, the experi- 
ment should be performed under a hood or out of doors. The reaction 
which takes place is represented by the equation, — 

C 7 H 7 .S0 2 ONa + PC1 S = C 7 H 7 .S0 2 C1 + POCl 3 + NaCl. 

After the action is over, and the mass cooled down to the ordinary 
temperature, add about a litre of cold water. Everything will dissolve 
except the sulphon-chloride, C 7 H 7 . S0 2 C1, which will remain as a heavy 
oil at the bottom of the vessel. Pour off the water, add about 500 cc of 
strong ammonia, and let stand. The chloride will thus be converted 
into the corresponding sulphon-amide, thus : — 

C 7 H 7 . S0 2 C1 + 2 NH 3 = C 7 H 7 . S0 2 NH 2 + NH 4 C1. 

After cooling, filter off the sulphon-amide ; wash well with cold water, 
and crystallize from water. 

Note for Student. — Refer back to what was said regarding the 
acid chlorides and acid amides, paying particular attention to the 
general methods of preparation and their decompositions. 

Experiment 65. Mix 20" potassium cyanide with an equal weight 
of dry potassium toluene-sulphonate, and distil from a small retort. 
The distillate is impure tolyl cyanide, C 7 H 7 . CN : — 

Cl ^l > S0 2 + KCN = C 7 H 7 .CN + K^SOg. 

Put the tolyl cyanide in a flask of 300 cc to 400 cc capacity, and add a mix- 
ture of 50 cc water and 150 cc ordinary concentrated sulphuric acid. Heat 
on a sand-bath until the toluic acid begins to appear in the form of fine, 
white needles in the neck of the flask. On cooling, the acid will crys- 
tallize out. Pour off the liquid, and wash with cold w 7 ater. Now 
crystallize the acid once or twice from water. When pure, para- 
toluic acid melts at 177°. The reaction is represented by the fol- 
lowing equation : — 

C 7 H 7 .CN + 2 H,0 = C 7 H 7 .C0 2 H + NH 3 . 
BeDzene-sulphonic acid itself is a very easily soluble sub- 



270 DERIVATIVES OF THE BENZENE SERIES. 

stance. It is a strong acid, and yields a series of salts and 
other derivatives. 

When fused with potassium hydroxide, benzene-sulphonic 
acid is converted into phenol (Exp. 66, p. 272) : — 

C 6 H 5 .S0 3 K + KOH = C 6 H 5 .OH + K 2 S0 3 . 

By further treatment of benzene with fuming sulphuric acid 
a benzene-disulphonic acid is formed. This is capable of the 
same transformations as the mono-sulphonic acid. 

Note for Student. — By what reaction could benzene-disulphonic 
acid be transformeclinto the corresponding dicarbouicacid,C 6 H 4 (C0 2 H) 2 ? 
Suppose the product obtained were meta-phthalic acid, what conclusion 
could be drawn with reference to the relation of the two sulpho groups, 
S0 3 H, in the disulphonic acid ? 

Phenols, or Hydroxyl Derivatives of Benzene, etc. 

The hydroxji derivatives of the paraffins are called alcohols. 
As will be remembered the}- are of three kinds, each of which 
is characterized by certain properties. These are : — 

1. Primary alcohols of which ordinary ethyl alcohol is the 
commonest example, and which, when oxidized, yield aldehydes 
and then acids containing the same number of carbon atoms. 

2. Secondary alcohols, which by oxidation yield acetones and 
then acids containing a smaller number of carbon atoms. 

3. Tertiary alcohols, which by oxidation yield neither alde- 
hydes nor acetones, but break down at once, yielding acids 
with a smaller number of carbon atoms. 

The primarv alcohols were shown to correspond to the 

TT I TS 

formula C \ ; the secondary to C -j ; and the tertiary to 



-R 



c \ -r. } or 5 ^ n °ther words, the primary alcohols contain the 

1 HO 
group CH 2 .OH; the secondary, the group CH.OH; and the 

tertiary, the group C.OH. 



MON-ACID PHENOLS. 271 

Now, the simplest hydroxyl derivative of the members of 
the benzene series is phenol, C 6 H 5 .OH, or benzene in which one 
hydrogen is replaced by hydroxyl. Representing this com- 
pound in terms of the accepted benzene hypothesis, we have 

the formula 

OH 

H(T X CH 

I i 

HO \ / OH 

H 

According to this, phenol appears to be allied to the tertiary 
alcohols, as it contains the group C.OH, and not CH 2 OH nor 
CH.OH. We shall see that, in fact, phenol conducts itself 
towards oxidizing agents like the tertiary alcohols. 

All compounds which contain hydroxyl in the place of the 
benzene-hydrogen atoms of benzene and its homologues are 
called phenols. As in the case of alcohols, there are phenols 
containing one hydroxyl, or mon-acid phenols ; those containing 
two hydroxyls, or di-acid phenols ; those containing three hy- 
droxyls, or tri-atid phenols, etc. Some of these are familiar 
substances. 

Mon-acid Phenols. 

Phenol, carbolic acid, C 6 H 6 0(= C 6 H 5 OH). —Phenol is 
found in nature in small quantities in the urine. It is formed 
by the distillation of wood, coal, and bones. Hence, it is a 
constituent of coal tar, and from this it is prepared. For this 
purpose the heavy oil (see p. 233) is treated with an alkali 
which dissolves the phenol. From the solution it is precipitated 
by hydrochloric acid. It is purified by distillation. 

Phenol can also be made by converting nitro-benzene into 
aniline ; then into diazo-benzene, and boiling this with water 
(see Exp. 62 (&)) ; and by melting benzene-sulphonic acid 
with potassium hydroxide. 



272 DERIVATIVES OF THE BENZENE SERIES. 

Experiment 66. In a silver (or iron) crucible, or evaporating dish, 
melt 40s to 50s potassium hydroxide, after adding a few cubic centi- 
metres of water. Now add gradually 10§ finely- powdered sodium 
toluene-sulphonate, obtained in Exp. 63, stirring constantly with a silver 
(or iron) spatula. Do not heat to a very high temperature. After the 
mass has been kept in a state of fusion for one-quarter to one-half an 
hour, let it cool. Dissolve in 200 cc to 250 cc water, and acidify with 
hydrochloric acid. Notice the odor of the gases given off. What gas 
do you detect? When the liquid has cooled down, extract with ether 
in a glass-stoppered cylinder. From the ether extract distil the ether 
on a water-bath. The residue is impure cresol (p. 276). Phenol can 
be detected by the following reactions, for which a solution in water 
should be prepared : — 

(a) A few drops of ferric chloride solution gives a beautiful blue 
color. 

(&) Add one-fourth volume of ammonia, and then a few drops of 
a dilute solution of bleaching powder. A blue color is produced. 

(c) Bromine water gives a yellowish-white precipitate of tri-brom- 
phenol. 

The reaction which takes place in melting potassinm hydrox- 
ide and potassium benzene-sulphonate together is represented 
by the equation, — 

C 6 H 5 .S0 3 K -f KOH = C 6 H 5 .OH + K 2 S0 3 . 

It effects the replacement of the sulpho group, S0 3 H, by 
hydroxyl. 

Phenol, when pure, crystallizes in beautiful colorless rhombic 
needles. The presence of a little water prevents it from solidi- 
fying. It has a peculiar, penetrating odor ; boils at 180° ; is 
difficultly soluble in water (1 part in 15 parts water at ordinary 
temperature) ; mixes with alcohol and ether in all proportions ; 
and is poisonous. 

Phenol forms compounds with several metals. Among these 
may be mentioned the following : — 

Potassium phenolate, C G H 5 .OK, made by dissolving potassium 
in phenol, and by treating phenol with caustic potash. 

Barium phenolate, (C 6 H 5 0) 2 Ba -f- 2 H 2 0, made by dissolving 
phenol in baryta water. 



PHENYL ACETATE. 273 

Lead oxide phenol, C 6 H 6 O.PbO, made by dissolving lead 
oxide in phenol. 

It also forms ethers, of which the methyl and diphenyl 
ethers may serve as examples : — 

Methyl-phenyl ether, 7 H 8 o(= ^ 5 > o). — This sub- 
stance, also called anisol, is obtained from anisic acid (methoxy- 
benzoic acid) by boiling with baryta water. It is made also by 
treating potassium phenolate, C 6 H 5 OK, with methyl iodide : — 

C 6 H 5 OK + CH 3 I = ^ 5 >0 + KI. 
U±l 3 

It is a liquid of a pleasant odor. 

Note for Student. — Compare this substance with ordinary ether. 
What method analogous to that above mentioned can be used in the 
preparation of ordinary ether? 

Diphenyl ether, C 12 H ]0 of= ^ 6 ^ 5 > o). — This bears to 

phenol the same relation that ordinary ether bears to alcohol. 
With acids, phenol, like the alcohols, yields ethereal salts in 
which the phenyl group, C 6 H 5 , takes the place of a metal. 
Among the compounds of this class which phenol forms with 
organic acids, the following may be mentioned : — 

Phenyl acetate, CgH 8 2 (=CH 3 .C0 2 .C 6 H 5 ).— This is formed 
by treating phenol with acetyl chloride. 

Note for Student. — What use is acetyl chloride put to as a re- 
agent in organic chemistry? Explain its use. What conclusion can 
be drawn from the fact that acetyl chloride acts upon phenol, replacing 
one hydrogen by acetyl, C 2 H 3 0? 

Substitution-products of phenol. Phenol is very susceptible 
to the action of various reagents, and a large number of substi- 
tution-products have been made from it. 

Bromine acts upon it readily. If, for example, bromine water 



274 



DERIVATIVES OF THE BENZENE SERIES. 



is added to a water solution of phenol, tri-brom-phenol is formed 
and precipitated. 

Dilute nitric acid acts upon phenol, yielding two mono-nitro- 
phenols, C 6 H 4 | 2 , one of which has been shown to belong to 
the ortho series, the other to the para series. 

Experiment 67. Add 20s pheDol to a mixture of 80 cc water and 
4r0 cc ordinary concentrated nitric acid (sp. gr. 1.34). Stir, and, after a 
time, pour off the dilute acid from the oil. Wash with water, and then 
put it into a flask, with about a litre of water, arranged as shown in 
Fig. 15. Flask A holds nothing but water; while the oil, together with 




Fig. 15. 

water, are in B. From A a current of steam is passed into B, which 
is heated by means of a lamp. Yellow crystals pass over and appear 
in the receiver, while a non-volatile substance remains behind in flask 
B. The volatile substance is ortho-nitro-phenol ; the non-volatile is 
para-nitro-phenol. 

Tri-nitro-phenol, picric acid, C 6 H 3 N 3 7 ( = C G H- 1 2 

This is formed very easily by the action of strong nitric acid on 
phenol. 

Experiment 68. Add 10s phenol slowly to 10s concentrated nitric 
acid. When the action is over, add 30° fuming nitric acid and boil 



PHENYL MERCAPTAN. 275 

for some minutes. Extract the picric acid by means of hot water; 
and purify by dissolving in potassium carbonate, and evaporating to 
crystallization. 

Picric acid forms yellow crystals, has a very bitter taste, 
is poisonous, decomposes with explosion when heated rapidly. 
It dyes wool and silk yellow. 

Note for Student. — Is there any analogy between tri-nitro- 
phenol and tri-nitro-glycerin? What is the essential difference be- 
tween them? 

One of the most interesting properties of tri-nitro-phenol is 
its power to form salts. It acts like a strong acid. It will 
thus be seen, that, while the substance C 6 H 5 .OH has only very 
slight acid properties, the same substance, with three of its 
hydrogens replaced by nitro groups, C 6 H 2 (N0 2 ) 3 .OH, has 
strong acid properties. In the salts, which have the general 
formula C 6 H 2 (N0 2 ) 3 .OM, the metals replace the hydrogen of 
the hydroxyl. Among them may be mentioned the potassium 
salt which was obtained in Exp. 68 ; this explodes when heated 
and when struck. Ammonium picrate, C 6 H 2 (N0 2 ) 3 .ONH 4 , is 
used as a constituent of explosives. 



Phenyl mercaptan, ) __ OT _. . 

■d, ,, , , , ., VC 6 H 6 S(=C 6 H 5 .SH). — This bears 

Phenyl hydrosulphide, J 

the same relation to phenol that mercaptan bears to alcohol. 

It can be made by reducing benzene-sulphonic acid. This 

reduction is effected by first making the sulphon-chloride, 

C 6 H 5 .S0 2 C1, (Exp. 64), and then treating this with nascent 

hydrogen. 

Note for Student. — What is the effect of oxidizing the mercap- 
tans? 

It can be made, also, by treating phenol with phosphorus 
pentasulphide, the effect of this reagent being to replace oxy- 
gen by sulphur. 



276 DEBIVATIVES OF THE BENZENE SERIES. 

Note for Student. — What analogy is there between the action oi 
phosphorus pentachloride and of phosphorus pentasulphide on com- 
pounds containing oxygen? 

Phenyl mercaptan is a liquid, with a very disagreeable 
odor. With mercuric oxide it forms a crystallized com- 
pound, (C 6 H 5 S) 2 Hg. 

Cresols, C 7 H 8 Of = C 6 H 4 < ^J J. — There are three cresols, 

■ CH 

or hydroxyl derivatives of toluene, of the formula C 6 H 4 < 3 . 

They are all found in coal tar, and the tars from pine and beech 
wood. When mixed together, it is difficult to separate them. 
To obtain them in pure condition, it is therefore best to make 
them from the three toluidines, or from the three sulphonic acids 
of toluene. 

Note for Student. — Give the equations representing the reactions 
involved in passing from the three toluidines to the cresols, and from, 
the three toluene-sulphonic acids to the cresols. 

The cresols resemble phenol very closely. 

Creosote is a mixture of chemical compounds contained in 
wood tar. It contains the cresols. Coal-tar creosote consists 
largely of phenol. 

CH 3 m 
Thymol, propyl-meta-cresol, C 10 H u O( = C 6 H 8 



ro.n.3 \i 

U OHW . 
Ic 3 H,(pV 



This phenol is contained in oil of thyme, together with cymene. 
It forms large monoclinic crystals, which melt at 50°. It has a 
pleasant odor, like that of the oil of thyme. Treated with phos- 

1 Formulas of this kind serve very well to indicate the relations of the groups and 
atoms contained in henzene derivatives. This one, for example, indicates that the 
hydroxyl is in the meta position (m) to methyl; while the propyl is in the para 
position to methyl (p). For di-suhstitution products, such formulas may also 

PTT 

be used. Thus, the three toluidines may be represented by C 6 H 4 < 3 

C 6 H 4 < CH3 , and C 6 H 4 < CH 3 . 



DI-ACID PHENOLS. 277 

phorus pentoxide, it yields meta-cresol ; while, when treated 
with phosphorus pentasulphide, it yields cyniene. These two 
reactions indicate that the groups contaiued in thymol bear to 
each other the relations indicated by the formula given above. 
It is one of the two theoretically possible hydroxyl derivatives 
of C3'mene. The other one, carvacrol, has the hydroxyl in the 
ortho position relatively to methyl. It has been made from 
the corresponding cymene-sulphonic acid ; is found in nature 
in the ethereal oil of Origanum Mrtum ; and can be made from 
carvol, or the oil of caraway. 

Di-acid Phenols. 
The three theoretically possible di-hydroxyl benzenes, 

ATT 

C 6 H 4 < , are all well known. 



Pyrocatechin, j C 6 H s o/ = C G H 4 < OH 

Ortho-rii-hydroxy-benzene, / b s \ ° OEUo) 

This substance is a frequent product of the dry distillation of 
natural substances, — as of catechu, morintannic acid, etc., — 
and of the melting of resins with caustic potash. It can be 
made by melting ortho-iodo-phenol or ortho-phenol-sulphonic 
acid with caustic potash. It forms crystals, which melt at 
104°. It is easily soluble in water, alcohol, and ether. 

The dilute solution in water gives with ferric chloride a 
dark-green color, which becomes violet on the addition of a 
little sodium carbonate. 

Resorcin, ) CHe0 f = H < OH 

Meta-di-hydroxy-benzene, ) 6 6 \ 6 OH(»») 

Resorcin is formed by the melting of a number of resins with 

caustic potash, as of galbanum, sagapenum, asafcetida, etc. 

It is made, also, by melting meta-iodo-phenol or meta-benzene- 

disulphonic acid with caustic potash. 

It crystallizes from water, usuallv in thick rhombic prisms 

Melting-point, "UtT. 



278 DERIVATIVES OF THE BENZENE SERIES. 

With ferric chloride, the water solution gives a dark purple 
color. Heated for a few minutes with phthalic acid in a test- 
tube, a yellowish-red mass is formed. When this is added 
to dilute caustic soda, a wonderfully fluorescent solution is 
obtained. The explanation of this reaction will be given 
under the head of Trl-phenyl-methane, when the phthaleins 
will be described. 

Resorcin is used largely in the manufacture of certain dyes, 
and is therefore manufactured on the large scale. 

ssrsr } **»*» (= °< h { !»• - H 

compound is formed by the action of nitric acid on resorcin, 
and on those resins which give resorcin when treated with 
caustic potash. It closely resembles picric acid. Heated 
with bromine and acetic acid, it yields the substance known 
as brompicrin, which has the formula C(N0 2 )Br 3 . 

Hydroquinone, 1 6 H 6 O ( = C 6 H 4 < OH \ 

Para-di-hydroxy-benzene, / 2 V 6 OHq?)/ 

Hj'droquinone is formed by the dry distillation of quinic acid, 
by reduction of quinone (which see), by the action of chromic 
acid on aniline, by melting para-iodo-phenol, etc. 

It is a crystallized substance which melts at 169° ; easily 
soluble in alcohol, ether, and hot water. 

Oxidizing agents, such as ferric chloride, chlorine, etc., con- 
vert it into quinone. 



It would lead too far to discuss here the reactions which 
have been made use of for the purpose of determining to which 
series each of the three di-hydroxy -benzenes belongs. The 
principle involved, however, is simple. Either these substances 
must be converted, directly or indirectly, into others, in regard 
to the relation of whose groups we have evidence ; or sub- 
stances, the relation of whose groups is known, must be con- 



TJRI-ACLD PHENOLS. 279 

verted into the di-hydroxy-benzenes. The reactions made use 
of for effecting the conversions are mainly those which have 
already been studied; viz., the formation of amido compounds 
from nitro compounds by reduction; the formation of diazo com- 
pounds from amido compounds ; the formation of (1) hydroxyl 
derivatives, (2) chlorine, bromine, or iodine derivatives, from 
the diazo compounds ; and the formation of hydroxyl deriva- 
tives from sulphonic acids. 



Orcin, I^tta/ nir fCH 



D^'droxy-toluene, } ***>>{' «M(Sb,> ~ There 
are three dye-stuffs, known as archil, cudbear, and litmus, which 
are made from different lichens by exposing them in powdered 
condition in ammoniacal solution to the action of air. They 
are treated with decomposing urine, from which the ammonia 
is obtained. Archil contains a substance called orcein, which 
can be made from orcin by treating it with ammonia. Orcin 
is contained in several lichens. It is formed, also, by melting 
aloes with caustic potash, and by melting chlor-toluene-sulpho- 
nic acid with caustic potash. The last reaction shows that 
orcin is a di-hydroxy-toluene. 

Orcin crystallizes in large, colorless, monoclinic prisms. 
Turns red in the air. Ferric chloride turns the aqueous 
solution deep violet. 

Treated with ammonia in moist air, it is converted into 
orcein, C 7 H 7 N0 3 , a substance which dissolves in alkalies, 
forming beautiful red solutions. 

Orcin is manufactured on the large scale, and then con- 
verted into orcein, which is used as a dye. 

Tri-acid Phenols. 
Pyrogallol, pyrogallic acid, 



Tri-hydroxy-benzene, ) C ^°^~ C ^ (OH) ^ 

Pyrogallic acid is formed by dry distillation of gallic acid, the 



280 DERIVATIVES OF TflE BENZENE SERIES. 

reaction being analogous to that by which benzene is produced 
by distillation of benzoic acid : — 

C 6 H 5 .C0 2 H = C 6 H 6 + C0 2 ; 

Benzoic acid. Benzene. 

C «M m H i' = C 6 H 3 (OH) 3 + C0 2 . 

t LU 2 H Pyrogallol. 

Gallic acid. 

It is formed also when one of the chlor-phenol-sulphonic acids 
is melted with caustic potash : — 

rOH rOH 

C 6 H 3 \ CI + ^X^ = C 6 H 3 } OH + KC1 + K 2 S0 3 . 



(s0 3 K K0H I OH 

Potassium chlor-phenol- Pyrogallol. 

sulphonate. 

It crystallizes in laminae or needles ; melts at 115° ; is easily 
soluble in water, ether, and alcohol. In alkaline solution it 
absorbs oxygen rapidly and becomes brown. On account of 
this power to absorb oxygen it is used in gas analysis. It is 
poisonous. 

With a solution containing a ferrous and a ferric salt it gives 
a blue color. 

Most of the phenols give color reactions with ferric chloride, 
and most of them change color in the air. These changes in 
color are undoubtedly due to the action of oxygen upon them. 
Towards oxidizing agents they are all unstable, most of them 
breaking down readily and yielding as the Chief product of 
oxidation, carbon dioxide. In general, the larger the number 
of hydroxyl groups contained in a phenol the less stable it is. 
We shall see that these same statements hold good for the 
hydroxy-acids of the benzene group, of which gallic acid and 
salicylic acid are examples. 

Alcohols of the Benzene Series. 

The phenols are those hydroxyl derivatives of the benzene 
hydrocarbons, which contain the hydroxyl in the place of one 
or more of the six benzene hydrogens. But just as there are 



BENZYL ALCOHOL. 281 

two classes of halogen substitution-products of toluene, in one 
of which the substitution has taken place in the benzene 
residue, and in the other in the marsh-gas residue, as indicated 
in the two formulas, — 

C 6 H 4 C1.CH 3 and C 6 H 5 .CH 2 C1, 

so, also, there are two classes of hydroxy 1 derivatives: (1) the 
phenols, and (2) those in which the hydroxy 1 is in the marsh- 
gas residue. The simplest example of the second class corre- 
sponds to the formula, C 6 H 5 .CH 2 .OH. It is isomeric with the 
cresols, C 6 H 4 .OH.CH 3 , and has entirely different properties. 
While the cresols are the true homologues of phenol, the new 
substance is really methyl alcohol in which one of the hydrogens 
of the methyl has been replaced by phenyl, C 6 H 5 . It may 




be represented by the formula, C i , when its analogy to 

fCH 3 

TT 

ethyl alcohol, CM , is at once apparent. 
i>OH 

Benzyl alcohol, C 7 H 8 0(= C 6 H 5 .CH 2 OH).— Benzyl alcohol 
or phenyl carbinol is found in nature in the balsams of Peru 
and Tolu, and in storax. In these substances it is, for the 
most part, in combination with benzoic or cinnamic acid.. It is 
made by treating the oil of bitter almonds, which is the corre- 
sponding aldehyde, with nascent hydrogen : — 

C 6 H 5 .CHO + H 2 = C 6 H 5 .CH 2 .OH. 

Oil of bitter almonds. Benzyl alcohol. 

It is also made by replacing the chlorine in benzyl chloride, 
C 6 H 5 .CH 2 C1, by hydroxyl, just as methyl alcohol is made from 
methyl chloride by a similar replacement. In the case of 
benzyl chloride this can be effected even by boiling for a long 
time with water : — 

C 6 H 6 .CH 2 C1 + H 2 = C 6 H 5 .CH 2 OH + HC1. 



282 DERIVATIVES OF THE BENZENE SERIES. 

Benzyl alcohol is a liquid with a pleasant odor. It hoils at 

206.5°. 

Note for Student. — Notice the great difference between the boil- 
ing-point of methyl alcohol and phenyl- methyl alcohol. 

Oxidizing agents convert the alcohol, first, into the oil of 
bitter almonds or benzoic aldehyde, and finally into benzoic 
acid. The relations between the three substances are like 
those between any primary alcohol and the corresponding alde- 
hyde and acid, as shown by the formulas, — 

C 7 H 8 0, C 7 H 6 0, C 7 H 6 2 , 

or C 6 H 5 .CH 2 OH ; or C 6 H 5 .CHO ; or C 6 H 5 .C0 2 H. 

Benzyl alcohol. Benzoic aldehyde. Benzoic acid. 

Hydriodic acid converts benzyl alcohol into toluene : — 
C 6 H 5 .CH 2 OH + 2 HI = C 6 H 5 .CH 3 + H 2 + 21. 

Benzyl alcohol conducts itself, in most respects, like the 
primary alcohols of the methyl alcohol series. A large number 
of its derivatives have been made and studied. Among them 
are ethereal salts, of which benzyl acetate, CH 3 .CO.OC 7 H 7 , and 
benzyl nitrate, N0 2 .OC 7 H 7 , may serve as examples; ethers, of 
which the methyl ether, C 6 H 5 .CH 2 .O.CH 3 , and the phenyl ether, 
C 6 H 5 .CH 2 .OC 6 H 5 , are good examples ; and substitution-products, 
of which chlor-benzyl alcohol, C 6 H 4 C1.CH 2 0H, and nitro-benzyl 
alcohol, C 6 H 4 (N0 2 ).CH 2 OH, are examples. 

These substitution-products are not made by direct treatment 
of the alcohol with the substituting agents, but by starting with 
the corresponding substituted toluene. Thus, chlor-benzyl 
alcohol is made from chlor- toluene, C 6 H 4 C1.CH 3 , b}- first con- 
verting this into chlor-benzyl chloride, C 6 H 4 C1.CH 2 C1, and then 
replacing the chlorine of the group CH 2 C1 by hydroxy 1. By 
oxidation the substituted benzyl alcohols yield the correspond- 
ing substituted benzoic acids : — 

C 6 H 4 C1.CH 2 0H + 2 = C 6 H 4 C1.C0 2 H + H 2 0. 

Chlor-benzoic acid. 

C 6 H 4 (N0 2 ).CH 2 OH 4- 2 = C 6 H 4 (N0 2 )C0 2 H 4- H 2 0. 

Nitro-benzoic acid. 



ALDEHYDES OF THE BENZENE SERIES. 283 

Very few of the alcohols analogous to benzyl alcohol have 
been prepared. Plainly, the homologies may be of two kinds : 

1. Those which are phenyl derivatives of the alcohols of the 
methyl alcohol series. Of this class, phenyl-ethyl alcohol, 
C 6 H 5 .CH 2 .CH 2 OH, the isomeric substance C 6 H 5 .CH. OH. CH 3 , 
and phenyl-propyl alcohol, C 6 H 5 .CH 2 .CH 2 .CH 2 OH, are ex- 
amples. Phenyl-propyl alcohol is of special interest on 
account of its connection with cinnamic acid (which see), 
which has come into prominence since it has been shown to be 
closely related to the interesting substances of the indigo group. 
It occurs in storax in the form of an ethereal salt, which will 
be spoken of more fully under the head of Cinnamic Acid. 

2. Those which are derivatives of xylene, mesitylene, etc., 
in the same sense as benzyl alcohol is a derivative of toluene. 
The following belong to this class : — 

Tolyl-carbinol .... C 6 H 4 < CH3 , 
* CHoOH' 

and Cuminyl alcohol .... C 6 H 4 < 2 , 

C 8 H 7 ( P ) 

which is made from cuminol, an aldehyde found in the oil of 
caraway. 

Aldehydes of the Benzene Series. 

The aldehydes of this group are closely related to the alco- 
hols just considered. The simplest one is the oil of bitter 
almonds, or benzoic aldehyde, C 7 H 6 0. 

Oil of bitter almonds, ) _ _ _, „ TT ~ TT/ -^ ™ . , 
^ . ini a VC 7 H 6 0(=C 6 H 5 .CHO).— Thissub- 

Benzoic aldehyde, > 

stance occurs in combination in amygdalin, which is found in 

bitter almonds, laurel leaves, cherry kernels, etc. Amygdalin 

belongs to the class of bodies known as glucosides, which break 

up into a glucose and other substances. Amygdalin itself, 

under the influence of emulsin, which occurs with it in the 



284 DERIVATIVES OF THE BENZENE SERIES. 

plants, breaks up into benzoic aldehyde, hydrocyanic acid, and 
dextrose : — 

QoH^NOn + 2 H 2 = C 7 H 6 + CNH + 2 C^CV 

Amygdalin. Benzoic aldehyde. Dextrose. 

Benzoic aldehyde can be made : 

1 . By oxidizing benzyl alcohol : — 

C 6 H 5 .CH 2 OH + O = C 6 H 5 .CHO + H 2 0. 

2. By distilling a mixture of calcium benzoate and calcium 
formate : — 

c 6 h 5 .co|omI 



H.iCOOM 



C 6 H 5 .CHO + M 2 C0 3 . 



3. By treating benzoyl chloride, the chloride of benzoic acid, 
with nascent hydrogen : — 

C 6 H 5 .C0C1 + H 2 = C 6 H 5 .CHO + HC1. 

4. By treating benzal chloride with water or mercuric oxide : — 

C 6 H 5 .CHC1 2 + H 2 = C 6 H 5 .CHO + 2 HC1. 

Note for Student. — Refer to the general methods for the prepara- 
tion of aldehydes. Which of the above reactions are used for the 
preparation of aldehydes in general? Which of the reactions throw 
light upon the nature of aldehydes, and their relation to alcohols? 

Benzoic aldehyde is prepared either from bitter almonds, 
which } T ield about 1.5 to 2 per cent; or from benzal chloride, 
according to reaction 4, above given. The latter method is 
employed in the artificial preparation of indigo. 

Benzoic aldehyde is a liquid having a pleasant characteristic 
odor. It boils at 179°; is difficultly soluble in water; is not 
poisonous. 

It unites with oxygen to form benzoic acid ; with hydrogen 
to form benzyl alcohol ; with hydrogen sulphide, ammonia, 
ammonium sulphide, alcohols, acids, anhydrides, and ketones. 
In short, its powers of combination with other substances are 



MONOBASIC ACIDS, C n H 2n _ 8 2 . 285 

almost unlimited. Hence, a very large number of derivatives 
are known. 

Cuminic aldehyde, cuminol, OioH r ,0[= C 6 H 4 < ~ TX 

V G 3 H T (i>) 

This aldehyde occurs in oil of carawa}^, from which it is made. 
It is a liquid with the odor of the oil of caraway. Its reactions 
are like those of benzoic aldehyde. 



Acids of the Benzene Series. 

The simplest of these acids has been referred to repeatedly. 
It is benzoic acid, which bears to benzene the same relation 
that acetic acid bears to marsh gas. It is the carboxyl deriva- 
tive of benzene. The homologous acids are the carboxyl 
derivatives of the homologous hydrocarbons. We shall find 
mono-basic, di-basic, tri-basic, and even hexa-basic acids, 
though the number of acids actually known is small. 



Monobasic Acids, C n H 2n _ 8 2 . 

Benzoic acid, C 7 H G 2 (= C 6 H 5 .C0 2 H). — Benzoic acid occurs 
in gum benzoin, in the balsams of Peru and Tolu, and in 
combination with amido-acetic acid or glycine in the urine of 
herbivorous animals. It can be made in many ways, the most 
important of which are given below : — 

1 . By oxidation of benz}l alcohol or any alcohol which is a 
phenyl derivative of an alcohol of the methyl alcohol series. 
The common condition in all these alcohols is the presence of 
the difficultly oxidizable residue, C 6 H 5 , in combination with an 
easily oxidizable residue of an alcohol of the marsh-gas series : — 

C 6 H 5 .CH 2 OH gives C 6 H 5 .G0 2 H ; 

C 6 H 5 .CH 2 .CH 2 OH " C 6 H 3 .C0 2 H ; 

C 6 H 5 .CH 2 .CH 2 ,CH 2 OH « C 6 H 5 .C0 2 H, etc. 



286 DERIVATIVES OF THE BENZENE SERIES. 

2. By oxidation of benzoic aldehyde, and the aldehydes of 
the other alcohols referred to in the preceding paragraph. 

3. By oxidation of all benzene hydrocarbons which contain 
but one residue of the marsh-gas series. Attention has already 
been called to this fact (see p. 248). 

4. By treating cyan-benzene (phenyl cyanide, benzo-nitrile) 
with a caustic alkali (see Exp. 65, p. 269) : — 

C 6 H 5 CN + KOH + H 2 = C 6 H 5 .C0 2 K + NH 3 . 

5. By treating benzene with carbonyl chloride in the presence 
of aluminium chloride : — 

C 6 H 6 + COCl 2 = C 6 H 5 .C0C1 + HC1; 

C 6 H 5 .C0C1 + H 2 = C 6 H 5 .C0 2 H + HC1. 

A reaction similar to this is of extensive application in the 
preparation of some hydrocarbons. It will be spoken of more 
fully under the head of Tri-phenyl-methane. 

6. By treating benzene with carbon dioxide in the presence 
of aluminium chloride : — 

CyHe + C0 2 = C 6 H 5 .C0 2 H. 

This and the preceding methods are of special interest from the 
scientific point of view, for the reason that they clearly show 
the relation between benzoic acid, on the one hand, and ben- 
zene and carbonic acid, on the other. 

Note for Student. — Which of the methods above given are of 
general application for the preparation of the acids of carbon? 

Benzoic acid is prepared on the large scale : (1) from gum 
benzoin by sublimation ; (2) from the urine of horses and 
cows by treating the hippuric acid with Irydrochloric acid ; 
(3) from toluene, best, b} r converting it into benzyl chloride, 
and oxidizing this with dilute nitric acid. 

Experiment 69. If the material is obtainable, evaporate a quantity 
of the urine of horses or cows to about one-half or one-third its vol- 



BENZOIC ACID. 287 

ume. Add hydrochloric acid. On cooling, hippuric acicl will be 
deposited. Recrystallize this several times from dilute nitric acid. 
Boil the hippuric acid for about a quarter of an hour with ordinary 
concentrated hydrochloric acid. By this means the hippuric acid is 
decomposed, yielding glycine (amido-acetic acid) and benzoic acid : — 

C 9 H 9 N0 3 + H 2 = C 7 H 6 2 + CH 2 < £ Q 2 

Hippuric acid. Benzoic acid. 2 

Glycine. 

Benzoic acid forms lustrous laminae or needles, which melt 
at 121°. 

Experiment 70. Determine the melting-point of the benzoic 
acid which you have made from hippuric acid. If it is not as 
stated above, recrystallize from water until the melting-point is not 
changed by further crystallization. Those specimens which are 
least pure can be purified by recrystallizing them from dilute nitric 
acid. 

The acid is comparatively easily soluble in hot water, but 
difficultly soluble in cold water. It is volatile with water 
vapor. 

Experiment 71. Put some in a one-litre flask, with about 700 cc 
to 800 cc water. Connect with a condenser, and boil down to about 
200 cc . Neutralize the distillate with ammonia, and evaporate down 
to a small volume. Acidify, when benzoic acid will be thrown 
clown. 

Its vapor acts upon the mucous membrane of the respira- 
tory passages, and causes coughing. 
It sublimes very easily. 

Experiment 72. Put some dry benzoic acid in a small, dry crys- 
tallizing dish, and put the dish in a sand-bath. Over the mouth of 
the dish put a paper cone made from filter-paper, arranged as shown 
in Fig. 16. Heat with a small flame. The benzoic acid will be depos- 
ited on the paper in beautiful lustrous needles. 

Or another form of apparatus, which is useful for subliming small 
quantities of substance, consists, essentially, of two watch-glasses 
which are of exactly the same size. The edges of the glasses are 
ground to secure a good joint when they are brought together. In 



288 



DERIVATIVES OF THE BENZENE SERIES. 



using this apparatus, put the substance to be sublimed in one of the 
glasses ; stretch a round piece of filter-paper over it, and then place 
the other glass upon it. Clamp the glasses together by means of a 
thin brass clamp. Now put the glasses on a sand-bath, and warm 




Fig. 16. 



gently, when the substance will slowly pass through the paper and 
appear in crystals in the upper watch-glass. It is well to keep a small 
pad of moist filter-paper on the upper glass during the operation. 

When heated with lime, benzoic acid breaks up into benzene 
and carbon dioxide (see Exp. 55) : — 

C 7 H 6 2 = C 6 H 6 4- C0 2 . 

With sodium amalgam, it yields benzyl alcohol and other reduc- 
tion-products. With hydrioclic acid, it yields toluene, and then 
hydrogen addition- products of toluene. 

A great many derivatives of benzoic acid are known. 



SUBSTITUTION-PRODUCTS OF BENZOIC ACID. 289 

Nearly all its salts are soluble in water. 
The ethereal salts can be made by any of the general 
methods already described. 

Note for Student. — What are the general methods for the prepa- 
ration of ethereal salts? 

Experiment 73. Dissolve 40» benzoic acid in 150 cc absolute alco- 
hol. Pass dry hydrochloric acid gas into the solution, keeping the 
latter cool by surrounding it with water. When the solution is 
saturated with hydrochloric acid, connect the flask with an inverted 
condenser, and warm gently on a water-bath for half an hour. Now 
add three or four volumes of water, when ethyl benzoate will separate 
as an oil. Wash with water and a little sodium carbonate ; and, finally, 
dry. 

Benzoyl chloride, C 6 H 5 .COCl, and bromide, C 6 H 5 .COBr, 
are made from benzoic acid in the same wa} 7 that acetyl chlo- 
ride is made from acetic acid. ■ They are more stable than the 
corresponding compounds of the fatty acids, but in general 
undergo the same kinds of change. 

Benzoyl cyanide, C 6 H 5 .CO.CN, is made by distilling mer- 
curic cyanide and benzoyl chloride : — 

2C 6 H 5 .C0C1 + Hg(CN) 2 = 2C 6 H 5 .COCN + HgCl 2 . 

The cyanogen can be converted into carboxyl, and thus an 
acid of the formula C 6 H 5 .CO.C0 2 H obtained. This is known 
as benzoyl-formic acid. It is of interest, for the reason that 
one of its derivatives is also a derivative of indigo (see 
Isatine) . 

Substitution-Products of Benzoic Acid. 

Benzoic acid readily yields substitution-products when treated 
with the halogens, nitric acid, and sulphuric acid. The products 
obtained by direct substitution belong mostly to the meta series. 
Thus, when chlorine acts upon benzoic acid, the main product 
is meta-chlor-benzoic acid; nitric acid gives mainly meta-nitro- 



290 DERIVATIVES OF THE BENZENE SERIES. 

benzoic acid; and sulphuric acid gives mainly meta-sulpho-ben- 
zoic acid. 

Note for Student. — Compare this with the result of the direct 
action of the same reagents on toluene. What are the first products 
of the action of nitric and sulphuric acids on toluene? 

Substituted benzoic acids can be made, also, by oxidizing 

the corresponding substituted toluenes. Thus, chlor-toluene 

gives chlor-benzoic acid ; nitro-toluene gives nitro-benzoic-acid, 

etc. : — 

C 6 H 4 C1 . CH 3 gives C C H 4 C1 . C0 2 H ; 

C 6 H 4 (N0 2 )CH 3 » C 6 H 4 (N0 2 )C0 2 H. 

The three nitro-benzoic acids and the corresponding amido- 
benzoic acids ma} 7 serve as examples of the mono-substitution 
products. 

r CO TT V 

Ortho-nitro-benzoic acid, C 7 H 5 NOJ = C 6 H 4 < NQ 2 J. 

Ortho-nitro-benzoic acid is formed, together with a large quan- 
tity of the meta acid and some of the para acid, by treating 
benzoic acid with nitric acid, by oxidizing ortho-nitro-toluene 
with potassium permanganate, and by oxidizing ortho-nitro- 
cinnamic acid. It crystallizes in needles, melts at 147°, and 
has an intensely sweet taste. 

CO TT 

Meta-nitro-benzoic acid, C 6 Hi < ^ rr ? is the chief prod- 

JNVJ 2 (m)' A 

uct of the action of nitric acid on benzoic acid. It crystallizes 
in laminae, or plates, and melts at 140° to 141°. 

CO TT 
Para-nitro-benzoic acid, C 6 H 4 < „J , is prepared best 

by oxidizing para-nitro-toluene. It crystallizes in laminae, 
melts at 238°, and is much less easily soluble in water than 
the ortho and meta acids. 

The determination of the series to which these three acids 






ISATINE. 291 

Deloug is effected by transforming them into the amido-acids ; 
and these, through the diazo compounds, into the corresponding 

ATT 

hydroxy-acids of the formula C 6 H 4 < CQ H - 

Note for Student. — Give the equations representing the action 
involved iu passing from toluene to ortho-hydroxy-benzoic acid (sali- 
cylic acid) by the method above referred to. 

In a similar way, lines of connection can be established 
between the three hydroxy-acids and the chlor-, brom-, and 
iodo-benzoic acids. 

Note for Student. — What are the reactions? 

The three hydroxy-acids, on the other hand, have been made 
by methods which connect them directly with the three dibasic 

acids of benzene, C 6 H 4 < C q 2 h - which, in turn, have been made 
from the three xylenes. 



Ortho-amido-benzoic acid, -> n _ ^ T ^ / pn ^ C0 2 H 
A J.X. -t J >0 7 ±i 7 JN <J 2 = 6 ±i 4 < ' 

Antnranilic acid, J V NH>(o) 

This acid is made by reducing ortho-nitro-benzoio acid with 

tin and hydrochloric acid, and by boiling indigo with caustic 

potash. It has already been stated that indigo yields aniline. 

Now, as ortho-amido-benzoic acid is also obtained, and this 

breaks up easily into aniline and carbon dioxide, 

C ^<^ 2 xr = C 6 H 5 .NH 2 + C0 2 , 
it seems probable that the aniline is a secondary product. 

Isatine, C 8 H 5 No/= C 6 H 4 <£j° >C.Oh)- — Isatine is ob- 
tained by the oxidation of indigo, and from ortho-amido- 
benzoic acid as follows : — 

The amido-acid is converted into the chloride, the chloride 
into the cyanide, and this into the corresponding carboxyl 



292 DERIVATIVES OF THE BENZENE SERIES. 

derivative, which is the orthoamido derivative of benzoyl- 
formic acid. The ortho-amido-benzoyl-formic acid thus ob- 
tained loses water, and is converted into isatine. The changes 
are represented by these equations : — 

(l)C 6 H 4 <£OOH +pcis =C6 H 4 <COCl ))+HC1 + POCl3; 

Ortho-amido-benzoic acid. Ortho-amido-benzoyl 

chloride. 

< 2 > C ^<S£» +^N = C 6 H 4 <^N + AgC1; 

Ortho-amido-benzoyl 
cyanide. 

(3) C 6 H 4 <™™ + 2H 2 = CeH 4 <COCOOH + ^ 

Ortho-amido-benzoyl- 
formic acid. 

(4) W<^jJ° H = C 6 H 4 <^° > C .OH + H 2 0. 

Isatine. 

The formula given for isatine represents it as an anhy- 
dride of ortho-amido-benzoyl-formic acid, the water which is 
given off being supposed to be formed by a union of the 
two hydrogens of the amido group and an oxygen of car- 
bonyl. The formation of anhydrides of aromatic acids is 
a characteristic of ortho compounds. Neither the meta nor 
para compounds give up water. We shall find that this fact is 

illustrated in the case of the dibasic acids, the only one which 

rooH 
yields an anhydride being ortho-phthalic acid, C 6 H 4 < , 

qq CUOH(o) 

which gives phthalic anhydride, C 6 H 4 < >0. This ready 

formation of anhydrides from ortho compounds, taken together 
with the fact that the meta and para compounds do not yield 
anhydrides, has been regarded as an argument in favor of the 
view that in the ortho compounds the two substituting groups 
are actually nearer together than in the meta and para com- 
pounds. 

The relation of isatine to indigo will be discussed briefly 
under the head of Indigo. 



HIPPURIC ACID. 293 

Meta- and Para-amido-benzoic acids are made from the 
corresponding nitro acids b}~ reduction. 

Hippuric acid, benzoyl-amido-acetic acid, 

C 9 H 9 N0 3 (= C 6 H 5 .0ONH.CH 2 CO 2 H). 
Hippuric acid, as has already been seen (Exp. 69), occurs in 
the urine of herbivorous animals, as the cow, horse, camel, and 
sheep. Some hippuric acid is found in human urine under 
ordinary circumstances. If benzoic acid is taken with the 
food, it appears as hippuric acid in the urine, while derivatives 
of benzoic acid appear as derivatives of hippuric acid. 

Hippuric acid can be made synthetically from benzoic acid 
and acetic acid : 

1. By heating glycine with benzoic acid to 160° : — 



C 6 H 5 .C0|0H! + '-^™>CH 2 = CH 2 <NH-CO.C 6 H 5 + ^ 

Hippuric acid. 

2. By heating benzamide with chlor-acetic acid : — 

C 6 H 5 .CO. NHH + ho ^ > CH 2 = ° A ' C °™ > CH 2 + HC1. 

Hippuric acid. 

3. By heating glycine with benzoyl chloride : — 

CH *<^5 + ci.oc.c 6 h 5 = ch 2 <™; t C0 - C6H5 + HC1. 

CU 2 M CD 2 H 

Hippuric acid ciystallizes from water in long, rhombic prisms. 

It is decomposed into benzoic acid and glycine by boiling 
with alkalies, and more readily by boiling with strong acids 
(Exp. 69) : — 

CH 2 <^C 7 H 5 + H2() = CH 2 <™ 2 h + C 6 H 5 .C0 2 H. 

Note for Student. — What relation does hippuric acid bear to 
benzamide? What is the effect of boiling acid amides with alkalies? 
Write the equation for the decomposition of benzamide, and compare 
it with that for the decomposition of hippuric acid. 



294 DERIVATIVES OF THE BENZENE SERIES. 

Toluic acids, C 8 H 8 2 . — There are four acids of this formula 
known ; viz. ; the three carboxyl derivatives of toluene in which 

the carboxyl takes the place of benzene hydrogen atoms, 

CH 

C 6 H 4 < 3 , and an acid obtained from toluene by replacing a 

hydrogen of the methyl by carboxyl, thus, C 6 H 5 .CH 2 .C0 2 H. 

CH. 

Ortlio-, meta-, and para-toluic acids, C 6 H 4 <r *_, are made 

C0 2 H 

by oxidizing the corresponding xylenes with nitric acid : — 
C 6 H 4 < <?s + 3 O = C 6 H 4 < <^ H + H 2 0. 

U±i 3 U±l 3 

They, as well as their derivatives, of which many are known, 
have been studied carefully. The substituted toluic acids can 
be made either b} T treating the acids with strong reagents or 
by oxidizing substituted xylenes : — 

C 6 H 3 (N0 2 )<^ 3 + 30 = CeH 3 (N0 2 )<^ H + H 2 0. 

Nitro-xylene. Nitro-toluic acid. 

o-Toluic acid, l Cs H s 2 (=C 6 H 5 .CH,C0 2 H).-Just 

Pnenyl-acetic acid, > 
as benzoic acid may be regarded as phenyl-formic acid, so 
a-toluic acid may be regarded as phenyl-acetic acid. It is 
obtained from mandelic acid, which is formed when amygdalin 
is treated with hydrochloric acid. It is prepared from toluene 
by converting this into benzyl chloride, from which the cyanide 
is made by boiling with potassium cyanide. The cyanide is 
then treated with an alkali, and yields the acid : — 

C 6 H 5 .CH 3 + Cl 2 = C 6 H 5 .CH 2 C1 + HC1 ; 

Boiling toluene. Benzyl chloride. 

C 6 H 5 .CH 2 C1 + KCN = C 6 H 5 .CH 2 CN +KC1; 

Benzyl cyanide. 

C 6 H 5 .CH 2 CN + 2H 2 = C G H 5 . CH 2 . C0 2 H + NH 3 . 

a-Toluic acid. 

The acid crystallizes in thin laminae ; and melts at 76.5°. 



HYDEO-CINNAMIC ACID. 296 

Note for Student. — What would you expect a-toluic acid to yield 
when oxidized? (See p. 248.) What would you expect it to yield 
when distilled with lime? What would you expect the three toluic 

CH 

acids, C 6 H 4 < 3 , to yield by oxidation, and when distilled with lime? 
C0 2 H 

(See p. 245.) 

Oxindol, C 8 H 7 NC)f = C 6 H 4 < ^ 2 > CoY — Oxindol is ob- 
tained by reduction of isatine (see p. 289) ; and also from 
ortho-amido-a-toluic acid by loss of water, in the same way 
that isatine is formed from ortho-amido-benzoyl-formic acid. 
When a-toluic acid is treated with nitric acid, the para- and 
ortho-nitro acids are formed. The latter is reduced by 
means of tin and hydrochloric acid, when oxindol is at once 
obtained : — 

CA< Sw 00H = c * h «<£S >co + h *°- 

Ortho-amido-a-toluic acid. Oxindol. 

Mesitylenic acid, C 9 H 10 o/= C 6 H 3 | Lq |4 2 )• — This acid 

has already been referred to as the first product of oxidation 
of mesitylene. It is the only monobasic acid which has been 
obtained from mesitylene ; and, according to the accepted 
hypothesis, it is the only one possible. By distillation with 
lime, it yields meta -xylene. 

Note for Student. — Of what special significance is the formation 
of meta-xylene from mesitylenic acid? 



Hydro-cinnamic acid |c 9 h 10 O 2 (=C 6 H 5 .CH 2 .CH 2 .CO 2 H). 

Phenyl-propionic acid, J 
Hydro-cinnamic or phenyl-propionic acid is obtained by treat- 
ing cinnamic acid with nascent hydrogen : — 

C 6 H 5 .CH.CH.C0 2 H + H 2 = C 6 H 5 . CH 2 . CH 2 . C0 2 H. 

Cinnamic acid, Hydro-cinnamic acid, 

Phenyl-acrylic acid. Phenyl-propionic acid. 



296 DERIVATIVES OF THE BENZENE SERIES. 

It is also made by starting with ethyl-benzene, C 6 H 5 .C 2 H 5 , and 
using the same reactions that are necessary to transform toluene 
into a-toluic acid (see p. 294). It is a product of the decay 
of several animal substances, such as albumin, fibrin, brain, etc. 
It crystallizes from water, in long needles, which melt at 47°. 
It yields benzoic acid when oxidized. 

Ortho-amido-hydro- i PTTx CH 2 .CH 2 .C0 2 H „. . ., 
cinnamic acid, } C &* < NH 2 (o) °~ Thls acid 

is prepared from hydro-cinnamic acid in the same way that 
ortho-amido-a-toluic acid is made from a-toluie acid. It is 
not obtained in the free state ; but, like the ortho-amido 
derivatives of benzoyl-formic and of a-toluic acids, it loses 
water, and forms the anhydride, 

Hydro-carbostyril, C 6 TLi < 9^ > CO — Hydro-carbo- 

NH 

styril is made by treating ortho-nitro-hydro-cinnamic acid with tin 
and hydrochloric acid. It is a solid which crystallizes in prisms, 
melting at 160°. It is interesting chiefly for the reason that it 
is closely related to the important compound quinoline (which 
see). When treated with phosphorus pentachloride, hydro- 
carbostyril is converted into di-chlor-quinoline. The signifi- 
cance of this reaction will appear later. 

Dibasic Acids, C n H 2n _i O 4 . 

The simplest acids of this group are the three phthalic acids, 
which are the di-carboxyl derivatives of benzene, belonging to 
the ortho, meta, and para series. 

acid was the first of the three acids of this composition dis- 
covered ; and, as it was obtained from naphthalene, it was 
named phthalic acid. In addition to its formation from 



PHTHALIC ANHYDRIDE. 297 

naphthalene may be mentioned that from alizarin and pur- 

CH 
purin; and from ortho-toluic acid, C 6 H 4 < C q 3 h(0 )? by oxida- 
tion with potassium permanganate. 

Experiment 74. Mix 40s naphthalene and 80s potassium chlorate, 
aud add this mixture gradually to 400s ordinary concentrated hydro- 
chloric acid. Naphthalene tetra-chloride, C 10 H 8 .C1 4 , is formed in this 
reaction. Wash with water. Gradually add 400s ordinary concen- 
trated nitric acid (sp. gr. 1.45), and boil in a large retort with upright 
neck. When all is dissolved, evaporate the nitric acid; and, finally, 
distil the residue. Phthalic anhydride passes over. Recrystallize from 
water. This will be used for other experiments. 

Phthalic acid forms rhombic crystals, which melt at 213° or 
lower, according to circumstances, as, when heated, it breaks 
up gradually, even below the melting-point, into water and the 
anhydride which melts at 128°. Distilled with lime, it yields 
benzene ; though, by selecting the right proportions, benzoic 
acid can be obtained : — 

(1) C 6 H 4 < <gg = C 6 H 6 + 2 C0 2 ; 

(2) C 6 H 4 < £0*g = CeH5 CQ . H + c()2 

Phthalic acid is decomposed by chromic acid, yielding only 
carbon dioxide and water. Hence, ortho-xylene, when treated 
with chromic acid, does not yield phthalic acid. By boiling 
ortho-xylene with nitric acid, however, it yields ortho-toluic 

PIT 

acid, c e H 4< co^HCo)' anc * ^ s can k e oxidized to phthalic 
acid by treatment with potassium permanganate. 



CO 

Phthalic anhydride, C 6 H 4 < C q>0, is formed by heat- 
ing phthalic acid. It forms long needles, which melt at 128°. 
Treated with phenols, it forms the compounds known as phtha- 
leftns (which see). 



298 DERIVATIVES OF THE BENZENE SERIES. 

Isophthalic acid, ) -, TT ^ 0O 2 H - , , 

Meta-phthalic acid, ! °° H *< CO.HW " f ° rmed by ° X1 " 
clizing either meta-xylene or meta-toluic acid with chromic 
acid ; by distilling meta-benzene-disulphonic acid with potas- 
sium cyanide, and boiling the resulting dicyanide with an 
alkali. 

Note for Student. — Write the equations representing the action 
involved in passing from meta-benzene-clisulphonic acid to isophthalic 
acid. Into which dihydroxy-benzene is this same disulphonic acid 
converted by melting it with caustic potash? 

The acid is formed, further, by treating meta-sulpho-benzoic 
acid with sodium formate : — 

0A< SS£-» + H - c ° 2Na = ca< co:k ( », + HNaso *- 

Potassium sulpho- Potassium iso- 

benzoate. phthalate. 

This reaction is of importance, for the reason that the same 
sulpho-benzoic acid, which is thus converted into isophthalic 
acid, can also be converted into one of the three hydroxy- 
benzoic acids ; and thus connection is established between 
the latter and isophthalic acid and meta-xylene. 

Isophthalic acid crystallizes in fine needles from water. It 
melts above 300°, and is not converted into an anhydride. 



Terephthalic acid, -» ~ TT 00 2 H ™ , ,, ,. ., 

Para-phthalic acid, I °« H ' < CO^)' - Tere P hthahc acld 

is formed by oxidation of the oil of turpentine, 1 cymene, para- 

x}dene, and para-toluic acid ; by heating a mixture of potassium 

para-sulpho-benzoate and sodium formate : — 

w< solL) + HWa - CA <coS(.) + HNaS ° 3 - 

Potassium para- Potassium tere- 

sulpho-benzoate. phthalate. 

1 The prefix tere is derived from the Latin terebinthinus, turpentine. 



PHENOL-ACIDS OF THE BENZENE SERIES. 299 

Para-sulpho-benzoic acid is converted into one of the three 
hydroxy-benzoic acids by caustic potash. In the para as welJ 
as the meta series, the lines of connection indicated below have 
been established : — 
ptt/ 0H P tt^C0 2 H CH /H 3 



I 



V 



CHc 



riTi- / C0 2 H prr / ^ x± 3 

C6H4< C0 2 H^^ C6H4< C0 2 H 



f 



„ TT OH . r „ , S0 3 H 

CcH 4<0H <— C ^< S O s H 

Terephthalic acid is a solid which is practically insoluble in 
water. It sublimes without melting and, like isophthalic acid, 
yields no anhydride. 

Hexabasic Acid. 

Mellitic acid, Ci 2 H 6 12 [= 6 (CO 2 H) 6 ]. — This acid occurs 
in nature in the form of the aluminium salt, as the mineral 
honey-stone or mellite. The mineral is rare, and is found in 
beds of lignite. Mellitic acid has been made by direct oxida- 
tion of carbon with potassium permanganate, and by oxidation 
of hexa-methyl-benzene, C G (CH 3 ) 6 . By ignition with soda-lime 
it is converted into benzene and carbon dioxide : — 

C G (C0 2 H) 6 = C 6 H 6 + 6 C0 2 . 

Phenol-acids, or Hydroxy- acids of the Benzene Series. 

It will be remembered that the alcohol acids or hydroxy- 
acids of the paraffin series form an important class, including 
such compounds as glycolic, lactic, malic, tartaric, and citric 
acids. The peculiarity of these compounds is their double 
character. They are at the same time alcohols and acids, 
though the acid properties are more prominent than the alco- 



300 DERIVATIVES OF THE BENZENE SERIES. 

holic. The hydroxy-acids of the benzene series bear the same 
relations to the benzene hydrocarbons that the hydroxy-acids 
already studied bear to the paraffins. The simplest are those 
which contain one hydroxyl and one carboxyl in benzene, 

OH 
having the formula C 6 H 4 < . 

C0 2 H 

MONO-HYDROXY-BENZOIC ACIDS, C 7 H 6 3 . 

Salicylic acid, ) OH _ S 1* 1* 

Ortho-hydroxy-benzoic acid, > 6 4 C0 2 H(o)' 
acid is found in the form of an ethereal salt of methyl, in the 
oil of wintergreen, prepared from the blossoms of Gaultheria 
procumbens. It is formed in a number of ways, among which 
the following should be specially mentioned : — 

1. By converting ortho-amido-benzoic acid into the diazo 
compound, and boiling with water. 

Note for Student. — Give the equations representing the re- 
actions. 

2. By melting ortho-sulpho-benzoic acid with caustic potash. 
Note for Student. — Write the equation. 

3. By passing carbon dioxide over sodium phenolate heated 
to 180° : — 

2 C G H 5 .ONa + C0 2 = C 6 H 4 <°^ a + C 6 H 5 OH. 

4. By heating phenol with tetra-chlor-methane and alcoholic 
potash : — 

C 6 H 5 .OH -f CC1 4 + 6 KOH = C 6 H 4 < ^ + 4 KC1 + 4 H 2 0. 

5. By saponifying the methyl salicylate found in oil of 
wintergreen : — 

CA< cS 2 CH 3 + K ° H= C ^<Zk + ° Hm - 



SALICYLIC ACID. 



301 



Experiment 75. Boil 30 cc to 40 cc oil of wintergreen with moder- 
ately strong caustic potash in a flask connected with an inverted con- 
denser. When it is dissolved, acidify with hydrochloric acid. Filter 
off the salicylic acid which separates, and re crystallize from water. 

Experiment 76. Dissolve 80s sodium hydroxide and 40* phenol in 
130 cc water in a litre flask, arranged as in Fig. 17. If the mixture is 
cool, heat to 50-60°, and remove the flame. Slowly acid 60s chloroform, 
shaking the mixture for several minutes after each addition. The mix- 
ture gradually becomes dark colored. An hour or more may be required 




Fig. 17. 



to complete the addition of all the chloroform. When the action is 
over, boil for an hour, and then distil off the excess of chloroform on 
the water-bath. Acidify with dilute hydrochloric acid, when a thick 
reddish brown oil comes clown. Distil in steam as in Exp. 67, until the 
distillate no longer appears in milky drops. A light-colored oil con- 
sisting of salicylic aldehyde and phenol settles in the receiver. Decant 
the supernatant water. Extract with ether, and concentrate the extract 
by evaporation in a water-bath. To the concentrated extract add a satu- 
rated solution of mono-sodium sulphite (freshly prepared by dissolving 



302 DERIVATIVES OF THE BEKZEKE SERIES. 

40s sodium sulphite in 75 cc hot water, cooling the solution, and satu- 
rating with sulphur dioxide). Shake the mixture 8 or 10 times, 2 or 
3 minutes at a time, for half an hour; then allow it to stand for sev- 
eral hours. The aldehyde unites with the sulphite, forming small, 
glistening, white crystals, while the phenol remains in solution in the 
ether. Filter with the aid of a pump, and wash the crystals with alcohol. 
Then treat the crystals on the water-bath with hydrochloric acid, when 
salicylic aldehyde is thrown down. Extract completely with ether, sepa- 
rate the two solutions, and evaporate the ether. 

In an iron or silver dish, melt 25s caustic potash; remove the lamp ; 
and add the salic3 r lic aldehyde drop by drop, stirring constantly. The 
potassium salt of salicylic acid is thus formed. After the mass is 
cooled, dissolve in water, and precipitate the salicjdic acid with dilute 
hydrochloric acid. Filter, wash with cold water, and purify by recrys- 
tallizing from water. 

The action of chloroform on phenol in the presence of caustic 
soda is analogous to that of tetra-chlor- methane. It will be 
understood with the aid of the following equations : — 

(1) C 6 H 5 .0H + CHC1 3 =C 6 H 4 <^ 1 +HC1; 

< 2 > C ^<cSd 2 + 2Na ° H = CA< cS(OH) 2 + 2NaCl! 

< 3 > C « H '<c2(OH) 2 = CA< So +H * a 

This reaction is of general application to phenols, and affords 
a very convenient method for the preparation of the phenol- 
acids. 

Salicylic acid crystallizes from hot water in fine needles. It 
melts at 155° to 156°. 

When heated, it breaks up into phenol and carbon dioxide : — 

C 6 H 4 < £J H = C 6 H 5 .OH + C0 2 . 

With ferric chloride, its aqueous solution gives a characteristic 
dark violet-blue color. Free salicylic acid is antiseptic, prevent- 



SALICYLIC ACID. 303 

ing decay and fermentation. It is therefore used for preserving 
organic substances. 

OH 
Salicylic acid forms salts of the general formula C 6 H 4 < ; 

and, with the alkalies, compounds, in which both the phenol hy- 
drogen and the acid hydrogen are replaced by metals, as 

C 6 H 4 < z~~ . Salts of the latter order, which contain the 
C0 2 K 

metals of the alkaline earths, are decomposed by carbon 

dioxide. Salicylic acid forms ethereal salts of the general 

formula C 6 H 4 < _,_ _, of which methyl salicylate, C 6 H 4 < nn n , 
C0 2 ^ " ou 2 u±± 3 

is the best-known example. It forms, also, ether-acids of the 
general formula C 6 H 4 < ; and, finally, compounds of the 

j-yp 

general formula C 6 H 4 < . 

A very large number of substitution-products and other 
derivatives of salicylic acid have been studied ; but they need 
not be considered here. 

That salicylic acid belongs to the ortho series, follows from 
the following facts : — 

Ortho-toluene-sulphonic acid has been converted into ortho- 
sulpho-benzoic acid, and this into salicylic acid. Further, the 
same toluene-sulphonic acid has been converted into ortho-toluic 
acid, which, by oxidation, yields phthalic acid. 

Ortho-toluene-sulphonic Ortho-sulpho-benzoic 

acid. acid. 

< 2) c ^<s2k(o) +KOH==CA< ohJ, + k * so ° ; 

Potassium salicylate. 

(3) w< SW) +KCN=CA< S(o, +KSO >-> 



304: DERIVATIVES OF THE BENZENE SERIES. 

(4) C 6 H 4 <CH 3 +2H3 = C6 H 4 <^ (())tN H 8 

Ortho-toluic acid. 

(5) C 6 H 4 < ™* , 3 = c 6 H 4 < £0»H + ^ 

C0 2 H(o) C0 2 H(o) 

PLthalic acid. 



Oxybenzoic acid, IcH < OH 

Meta-hydroxy-benzoic acid, / 6 * C0 2 H(m)' 



} c ^<ca, H ^-- This 



acid is made from meta-amido-benzoic and meta-sulpho-benzoic 
acid by the usual reactions. 

It crystallizes from water in needles united to form wart-like 
looking masses. It gives no color with ferric chloride. Its 
connection with meta-phthalic (isophthalic) acid and meta-xylene 
is effected by means of the transformations tabulated on p. 299 ; 
that is to say, the same sulpho-benzoic acid which, by melting 
with caustic potash, yields oxybenzoic acid, by melting with 
sodium formate, yields isophthalic acid. Therefore oxybenzoic 
acid is a meta compound. 



Para-oxybenzoic acid, -> QH -p 

Para-hydroxy-benzoic acid, J 6 4 0O 2 H(jp)' 
oxybenzoic acid is formed from the corresponding amido and 
sulpho-benzoic acids ; by treating various resins with caustic 
potash ; from anisic acid (which see) , by heating with hydriodic 
acid ; by heating potassium phenolate in a current of carbon 
dioxide. 

Note for Student. — Notice the fact that, while sodium phenolate, 
when heated in a current of carbon dioxide, yields salicylic acid, 
potassium phenolate, under the same circumstances, yields para-oxy- 
benzoic acid. 

Its aldehyde is formed, together with salicylic aldehyde, by 
treating phenol with chloroform and caustic soda (see Exp. 76). 



PROTOCATECHUIC ACID. 305 

The reasons for regarding para-oxybenzoic acid as a mem- 
ber of the para series are similar to those which show that 
oxybenzoic acid is a meta compound. The same sulpho-benzoic 
acid which yields para-oxybenzoic acid, also yields terephthalic 
acid. 

Anisic acid, 1 C H < OCH3 . — Anisic 

Para-methoxy-benzoic 1 acid, i 6 4 COJI(p) 

OCH 
acid is formed by the oxidation of anethol, C 6 H 4 < 3 , a 

C 3 H 5 

phenol ether contained in anise oil. It is made by heating 
para-oxybenzoic acid with caustic potash and methyl iodide. 
As the formula indicates, it is the methyl ether of para-oxy- 
benzoic acid. 

Dl-HYDROXY-BENZOIC ACIDS, C 7 H 6 4 . 

Protocatechuic acid, C 6 H 3 | «^ ^, is a frequent product 
of the fusion of organic substances with caustic potash. Thus, 
the following substances, among others, yield it: oil of cloves, 
piperic acid, catechin, gum benzoin, asafcetida, vanillin, etc. 
It is made from sulpho-oxybenzoic acid, and from sulpho-para- 
oxybenzoic acids by fusing with caustic potash. 

Note for Student. — What analogy is there between the fact that 
protocatechuic acid is formed from sulpho-oxj'benzoic acid and from 
sulpho-para-oxybenzoic acid, and the fact that pseudocumene is formed 
from brom-meta-xylene and from brom-para-xylene? What conclusion 
may be drawn regarding the relations of the two hydroxyl groups, and 
the carboxyl in protocatechuic acid? 

By distillation with lime, protocatechuic acid breaks up into 
pyrocatechin and carbon dioxide : — 

rOH 
C 6 lUOH = c,hJ°^ + C0 2 . 
( rn w * (JH 

V ^W 2 tl Pyrocatechin. 

1 Methoxy is derived from methoxyl, the name given to the ether group, OCH 3 . In 
a similar way OC 2 H 5 is called ethoxyl ; OC G H 5 , phenoxyl, etc. 



306 DERIVATIVES OF THE BENZENE SERIES. 

rOCH 3 
Vanillic acid, C 6 H 3 -J OH , is formed by oxidation of 

LCCXH 
vanillin, which is the corresponding aldehyde. It is the mono- 
methyl ether of protocatechuic acid. 

/ c OCH 3 x 

Vanillin, 8 H 8 O 3 (= C 6 HJ OH ), occurs in nature, as a 
^ I CHO J 

crystalline coating, on the fruit of the vanilla. It is made 

A/~(TT 

artificially by treating the ether, C 6 H 4 < 3 , with chloroform 
and caustic soda. 

Tri-hydroxy-benzoic Acids, C 7 H 6 5 . 

Gallic acid, C 7 H 6 OJ = C 6 H 2 { co j| ). — Gallic acid occurs 

in sumach, in Chinese tea, and in many other plants. It is 
formed by boiling tannin or tannic acid with sulphuric acid ; by 
melting brom-protocatechuic acid with caustic potash : — 

rBr 
C 6 hJ (OH) 2 + KOH = C 6 H 2 j ^2 3 + KBr * 
(_C0 2 H lC ° 2H 

Brom-protocatechuic Gallic acid, 

acid. 

It is best prepared from gall nuts by fermentation of the 
tannin contained in them. 

Gallic acid is easily soluble in water. Its solution gives, 
with a little ferric chloride, a blue -black precipitate, which 
dissolves in excess of feme chloride, formiusj a dark oreeu 
solution. It readily reduces metallic salts in solution. When 
heated, it yields pyrogallol (pyrogallic acid) and carbon di- 
oxide : — f , nm 

C 6 H 2 j gj^j» = C 6 H 3 (OH) 3 + C0 2 . 

Tannic acid, tannin, Ci4H 10 O 9 . — This substance occurs 
in gall nuts, from which it is extracted in large quantities. It 
is an amorphous powder. It is markedly astringent in its action 



KETONES. 307 

on the mucous membranes. It is soluble in water, the solution 
giving, with ferric chloride, a dark blue-black color. TanDin is 
used extensively in medicine, in dyeing, and in the manufacture 
of ink. Its relation to gallic acid is indicated by the following 

2 C 7 H 6 5 = C 14 H 10 O 9 + H 2 0. 

Gallic acid. Tannin. 

Ketones and allied Derivatives of the Benzene Series. 

The ketones of the benzene series are strictly analogous to 
those of the paraffin series, and they are made in the same way. 
Acetone is made by distilling calcium acetate : — 



CH 3 .CO!0 Ca 
CH 3 J CO O 



CHs >CO -f CaC0 3 . 



CH 



3 
Acetone. 



So, also, benzophenone or diphenyl-ketone is made by distill- 
ing calcium benzoate : — 



C 6 H 5 .CO|0 c 

c 6 H 5 rcoo 



= C 6 H 5>C0 + CaC03> 

C 6 H 5 

Benzophenone. 

Further, by distilling mixtures of the salts of two fatty acids, 
mixed ketones are obtained : — 

CH 3 .CO:OMJ = CH 3 > co M2COa 
C 2 H 5 .;COOM! C 2 H 5 

° L J Ethyl-methyl 

ketone. 

And, similarly, mixed ketones containing one residue of a 
benzene Irydrocarbon and one of a paraffin ; or, two different 
residues of benzene hydrocarbons can be obtained thus: — 

(\\ C 6 H 5 .COOM _ C 6 H 5 m M m . 



C 6 H 5 .COOM 



Phenyl-raethyl ketone, 
Acetophenone. 



(2) r „ OH 3 =^>CO + M 2 C0 8 . 

Phenyl-tolyl-ketone. 

The individual ketones need not be considered. 



308 DERIVATIVES OF THE BENZENE SERIES. 

QUTNONES. 

The quinones are peculiar bodies which in some ways are 
allied to the ketones. The simplest example of the class, and 
the one best known, is called quinone. Its formula is C 6 H 4 2 , 
and it therefore appears to be benzene in which two hydrogen 
atoms are replaced by two oxygen atoms. All quinones bear 
this relation to the hydrocarbons, of which they may be regarded 
as derivatives. 

Quinone, C 6 H 4 2 , is formed by the oxidation of quinic acid, 
hydroquinone, para-diamido-benzene, and some other benzene 
derivatives in which two substituting groups occupy the para 
position relatively to each other. 

It forms long, yellow prisms ; sublimes in golden-yellow 
needles. 

Hydriodic acid reduces quinone to hydroquinone : — 

C 6 H 4 2 + 2 HI = C 6 H 4 (OH) 2 + 2 I. 

The easy transformation of hydroquinone into quinone, and 
the opposite transformation of quinone into hydroquinone, as 
well as the formation of quinone from other para compounds, 
force us to the conclusion that the oxygen atoms in quinone 
are in the para position relatively to each other. Quinone 
appears, therefore, as a substance containing two carbonyl 
groups which are united by means of hydrocarbon residues, 
as indicated in the formula, — 



O 
HC X X CH 



C * H 2<^>C 2 H 2 or 

co HC X y CH 

X C X 

o 

A substance of this kind may be called a di-ketone, and may 
be regarded as derived from a dibasic acid in the same way that 



PYRIDINE BASES. 309 

a simple ketone is derived from a monobasic acid. Thus, the 

pooit 
calcium salt of an acid of the formula C H 2 < __ _„ ought, ac- 

LOOJti 

cording to this view, to yield quinone by distillation : — 



C2H2< :COO >C i 



C 2 H 2 < pQ > C 2 H 2 + 2 CaC0 3 . 



Several quinones have been studied. Under the head of 
Anthracene, we shall meet with an important one called anthra- 
quinone, which has been made by such reactions as prove it to 
be a di-ketone in the sense in which this expression is explained 
above. 

Pyridine Bases, C n H 2n _ 5 N. 

In the manufacture of bone-black, bones are subjected to dry 
distillation, when an oil passes over which is known as bone oil. 
This oil is a complex mixture of substances, several of which 
have, however, been isolated. Among the pure substances 
which have been obtained from bone oil may be mentioned 
pyridine, picoline, lutidine, and collicline. All these compounds 
contain nitrogen ; and, starting with pyridine, they form an 
homologous series : — 

Pyridine C 5 H 5 N. 

Picoline C 6 H 7 N. 

Lutidine C 7 H 9 N. 

Collidine C 8 H U N. 

Pyridine, C 5 H 5 N. — Besides being formed in the distillation 
of bones, pyridine has recently been made in several ways, 
some of which enable us to form a conception in regard to 
its relations to other substances which have been studied. 
Great interest in the substance and its derivatives has been 



310 DERIVATIVES OF THE BENZENE SERIES. 

aroused by the observation that several of the alkaloids which 
occur in nature, such as quinine, cinchonine, nicotine, etc., 
when oxidized, yield acids containing nitrogen, which bear to 
pyridine the same relations that benzoic, phthalic acids, etc., 
bear to benzene. Thus, by oxidizing nicotine, nicotinic acid is 
obtained. This has the formula C 6 H 5 N0 2 ; and, when distilled 
with lime, it breaks up into p}Tidine and carbon dioxide : — 

C 6 H 5 N0 2 = C 5 H 5 N + C0 2 . 

Nicotinic acid. Pyridine. 

This naturally leads to the conclusion that nicotinic acid is 
pyridine-carbonic acid, C 5 H 4 N.C0 2 H, which bears to pyridine 
the same relation that benzoic acid bears to benzene, acetic 
acid to marsh gas, etc. 

Pyridine is formed : — 

1. By treating iso-amyl nitrate with phosphorus pentoxide :— * 

C 5 H u .N0 3 = C 5 H 5 N + 3H 2 0. 

2. By conducting acetylene and hydrocyanic acid together 
through a tube heated to redness : — 

2 C 2 H 2 + HCN = C 5 H 5 N. 

It is a liquid with a peculiar, sharp, characteristic odor. It 
boils at 116.7°. 

It unites with acids forming salts. 

It has been suggested that pyridine is related to benzene -, 
and that it should be regarded as the hydrocarbon in which one 
of the six CH groups is replaced by a nitrogen atom, as repre- 
sented in the formulas 



HC 

I 

HC 



H 




H 


c v 




n 


X CH 

1 


and 


HC X X CH 

1 1 


/CH 




HC X /CH 


H 







TERPENES. 311 

This view has suggested various lines of investigation. Thus, 
if the above formula really represents the relations between 
benzene and pyridine, it is clear that the existence of three 
isomeric mono-substitution products of pyridine ought to be 
possible. Thus, there should be three methyl-pyridines or 
picolines, three pyridine-carbonic acids, etc. The three pico- 
lines should correspond to the formulas 



H 


H 


CH 3 


HC X X CH 

1 i 


HC X X C.CH 3 


HC X X CH 

i i 


I i 


N 


1 1 
HC X /CH 


Ortho-picoliae. 


Meta-picoline. 


Para-picoline. 



All three picolines are known; and, by oxidation, they are 
converted into the three pyridine-carbonic acids, C 5 H 4 N.C0 2 H ; 
and these, when distilled with lime, yield pyridine and carbon 
dioxide. 

The pyridine bases unite with two, four, or six atoms of 
hydrogen. The addition-products thus formed are believed 
to exist in the alkaloids. 

Piperidine. C 3 H n N, a base found in pipeline, a constituent 
of pepper, has been shown to be hexa-hydro-pyridine. 

Nicotine is probably of similar structure. 

Valuable results may be expected from the further investiga- 
tion of pyridine and its derivatives. 

Terpenes, C 10 H 16 . 

In nature, particularly in the coniferous plants, occur several 
isomeric hydrocarbons, which are known by the common name 
terpene. These substances are very susceptible to the action 
of reagents, and hence undergo many changes. One of the 
most common changes is polymerisation. Thus, when a terpene 
is heated in a sealed tube, or is shaken with concentrated sul- 



312 DERIVATIVES OF THE BENZENE SERIES. 

phuric acid, or with boron fluoride and other substances, it is 
converted into polymeric modifications of the formulas C^H^ 
and C20H32. The terpenes unite with hydrochloric and hydro- 
bromic acids, forming compounds, C 10 H 16 .HC1 and C 10 H 16 .2 HC1. 

Oil of turpentine, terebenthene, Ci Hi 6 . — This oil is 
obtained by distilling turpentine, a resinous substance which 
exudes from incisions in the bark of various species of the 
pine, larch, fir, etc., especially the pine. The oil consists 
largely of a hydrocarbon, C 10 H 16 . The oils obtained from dif- 
ferent species of trees differ somewhat in their properties. 

Among the more interesting chemical transformations of oil 
of turpentine, the following may be mentioned : It absorbs 
oxygen from the air ; dilute nitric acid oxidizes it readily, con- 
verting it into acetic, propionic, butyric, oxalic, para-toluic, 
terephthalic acids and some other acids ; bromine and iodine 
convert it into cymene. 

Oil of turpentine is used in the manufacture of varnishes on 
account of its solvent power for resins. It is also used in 
medicine. 

The reactions above enumerated indicate clearly that there 
is a close relation between cymene and oil of turpentine. This 
is shown by the fact that it is so readily converted into cymene, 
and that it yields para-toluic and terephthalic acids by oxida- 
tion. It has therefore been suggested that oil of turpentine is 
a hydrogen addition-product of cymene, of the formula 

CH 3 

CH HC X X CH 2 

W<; ( ^ or , , 

x cr 

C 3 H 7 

Our knowledge concerning the isomerism of the terpenes is 
as yet incomplete, though of late much light has been thrown 



CAMPHOR. 313 

upon this chapter of chemistry, and we may confidently look 
for further interesting results. 

Terpene hydrochloride, | c HC1 _ when . oohlor . c 

Artificial camphor, > J 

acid gas is conducted into oil of turpentine, a curious solid 
known as artificial camphor is formed. It looks like ordinary 
camphor, and has a very similar odor. When heated alone, or 
with bases, it gives off hydrochloric acid, and a terpene different 
from the oil of turpentine is formed. 



Camphor. 

Borneol, Borneo camphor, Ci H 18 O. — Borneo camphor 
is a substance found in cavities in a tree (Dryobalanops cam- 
phora) which grows in Borneo, Sumatra, etc. It can be made 
by treating ordinary camphor with sodium : — 

2 C 1( >H 16 + 2 Na = C 10 H 17 ONa + C 10 H 15 ONa. 

Ordinary Sodium compound Sodium compound 

camphor. of borneol. of ordinary 

camphor. 

The relation between the two kinds of camphor is shown better 
by the equation : — 

CaoH 16 -J- H 2 — C 10 H 18 O. 

Ordinary Borneol. 

camphor. 

Camphor, laurinol, Ci Hi 6 O — This is the substance ordi- 
narily called camphor. It is obtained in China and Japan from 
different species of the genus camphor a of the laurus family, by 
distilling the finely-cut wood with water vapor. It is purified 
by sublimation. 

Camphor forms hexagonal crystals ; melts at 175°, and boils 
at 204°. It is only slightly soluble in water ; easily soluble in 
alcohol. 

Boiled with iodine, hydriodic acid gas is given off and cymene 



314 DERIVATIVES OF THE BENZENE SERIES. 

is formed. Phosphorus pentoxide decomposes camphor into 
cymene and water : — 

C 10 H 16 O = C 10 H 14 + H 2 0. 

Camphor. Cymene. 

The same decomposition is effected by heating camphor with 
concentrated hydrochloric acid to 170°. It will.be seen that, 
as far as the composition is concerned, the difference between 
a terpene and camphor is one atom of oxygen : — 

CioH 16 . C 10 H 16 O. 

Terpene. Camphor. 

The relation between the substances is undoubtedly a close 
one, as is shown by the formation of cymene from both. It is 
stated that a substance closely resembling camphor has been 
made by oxidizing the terpene known as camphene, which is 
formed by shaking oil of turpentine with sulphuric acid. 



CHAPTER XVI. 

DI-PHBNYL-METHANB, TRI-PHENYL-METHANE, 

TETRA-PHENYL-METHANE, AND THEIR 

DERIVATIVES. 

As we have seen, toluene may be regarded either as mettryl- 
bwnzene or phenyl-methane. Of course, according to all that 
is known regarding similar substances, the two views are identi- 
cal. Regarding it, for our present purpose, as phenyl-methane, 

{ C 6 H 5 
TT 
H 

This suggests the possibility of the existence of such sub- 
stances as 

C 6 H 5 

C TT 

Di-phenyl-methane . C ■{ ^ 6ns , 



II 
CM 

Tri-phenyl-methane 



&^5 

C 6 H 5 
C 6 H 5 
H 
CcHr 



L 5 

I n tj 

and Tetra-phenyl-methane . . . . . . C < 6 5 . 

I C 6 H 5 

L C 6 H 5 

All these hydrocarbons are known, and the derivatives of 
tri-phenyl-methane are of special interest and importance. 
There is one reaction by means of which these Irydrocarbons 



316 DI-PHENYL-METHANE, ETC. 

can be made very readily. It has also been used for the synthe- 
sis of many other hydrocarbons. It depends upon the remark- 
able fact that, when a hydrocarbon is brought together with 
a compound containing chlorine, and aluminium chloride then 
added, hydrochloric acid is evolved, and union of the two 
substances is effected, the aluminium chloride not entering into 
the composition of the product. Thus, when benzene and 
benzyl chloride, C 6 H 5 .CH 2 C1, are brought together under ordi- 
nary circumstances, no action takes place ; but, if some solid 
aluminium chloride is added, reaction takes place according 
to the following equation : — 

C 6 H 5 .CH 2 C1 + C 6 H 6 = C 6 H 5 .CH 2 .C 6 H 5 -{- HC1, 

Di-phenyl-methane. 

and di-phenyl-methane is formed. 

Similarly, when chloroform and benzene are brought together 
in the presence of aluminium chloride, tri-phenyl-methane is 
formed according to this equation : — 

CHCI3 + 3 C 6 H 6 = CH(C 6 H 5 ) 3 + 3 HC1. 

Tri-phenyl-methane. 

Another method by which these hydrocarbons can be made, 
consists in heating a chloride and a hydrocarbon together in the 
presence of zinc dust. Thus, benzyl chloride and benzene give 
di-phenyl-methane when boiled with zinc dust ; and benzal 
chloride, C 6 H 5 .CHC1 2 , and benzene give tri-phenyl-methane : — 

C 6 H 5 .CHC1 2 + 2 C 6 H 6 = CH(C 6 H 5 ) 3 + 2 HC1. 

Only tri-phenyl-methane will be taken up here. 

Tri-phenyl-methane, d 9 H 16 [= OH(0 6 H 5 ) 3 ]. — This hydro- 
carbon can be made, as above described, from benzal chlo- 
ride and benzene, and from chloroform and benzene. It 
can also be made from benzal chloride and mercury diphenyl, 
Hg(C 6 H 5 ) 2 :- 

C 6 H 6 .CHC1 2 + Hg(C 6 H 5 ) 2 = CH(C 6 H 5 ) 3 + HgCl 2 . 



ANILINE DYES. 317 

It forms lustrous, thin laminae, which melt at 92°. It is 
insoluble in water ; easily soluble in ether and chloroform. It 
is crystallized best from alcohol. 

Towards reagents it is very stable. Thus, ordinary concen- 
trated sulphuric acid does not act upon it. r C 6 H 5 

J ri tt 

Oxidizing agents convert it into tri-phenyl-carbinol, C -! 6 5 - 

I OH 
That the oxidation-product is realty tri-phenyl-carbinol appears 
probable, from the fact that whenever aromatic hydrocarbons 
which contain paraffin residues are oxidized, the paraffin resi- 
dues are first attacked, while, as a rule, the benzene residue is 
unacted upon. 

Trinitro-triphenyl- | o l9 H 18 (N0 2 ) 3 [=CH(0 6 H 1 N0 2 ) 8 ], is 
methane, 
formed by treating tri-phenyl-m ethane with nitric acid ; and 
also by treating a mixture of nitro-benzene and chloroform 
with aluminium chloride : — 

CHCI3 + 3C 6 H 5 .N0 2 = CH(C 6 H 4 .N0 2 ) 3 -f- 3 HC1. 

This reaction shows that in the tri-nitro product one nitro group 
is contained in each benzene residue. 

Triamido-triphenyl-methane, para-leucaniline, 

C 19 H 13 (NH 2 ) 3 [= CH(C 6 H 4 . NH 2 ) 3 ]. 
The tri-amido compound is made by reduction of the tri-nitro 
compound, and also by reduction of para-rosaniline. It is 
converted into para-rosaniline by oxidation. 

Aniline Dyes. 

The well-known substances included under the head of Ani- 
line Dyes are more or less simple derivatives of the two 
compounds called rosaniline and para-rosaniline. 

When mixtures of aniline and toluidine are heated together 
with different oxidizing agents, such as arsenic acid, stannic 



318 DI-PHENYL-METHANE, ETC. 

chloride, mercuric chloride, etc., several substances are formed, 
the principal of which are the two above named. Para-rosani* 
line, Ci 9 H 19 N 3 0, is formed from para-toluidiue and aniline, accord- 
ing to the equation, — 

2 C 6 H 7 N + C 7 H 9 N + 30 = C 19 H 19 N 3 + 2 H 2 0. 

Aniline. Toluidine. Para-rosaniline. 

Rosaniline, C 20 H 21 N 3 O, is formed in a similar way : — 
C 6 H 7 N + 2 C 7 H 9 N +30 = C^H^O + 2 H 2 0. 

Aniline. Toluidine. Rosaniline. 

The composition and modes of formation of the two sub- 
stances show that rosaniline is a homologue of para-rosaniline, 
the relation between the two substances being represented by 
the formulas C ]9 H 19 N 3 and C 19 H 18 (CH 3 )N 3 0. 

By treating para-rosaniline with a reducing agent, it is con- 
verted into para-leucaniline, which has been shown to be tri- 

amido-triphenyl -methane : — 

/ C WH 4 • NEL 2x 

l„\ C 6 H 4 .NH 2 



C 19 H 19 N 3 + H 2 = C 19 H 19 N 3 ' = C { ^ ' ^ + H 2 0. 

Para-rosani- Para-leucA ^ 6 tl 4 .lN*l 2 / 

line. aniline. ^ I. JJ ' 



We see thus that para-rosaniline and rosaniline, which are 
the fundamental compounds of the group of aniline dyes, are 
derivatives of the hydrocarbon tri-phenyl-methane. 

Para-rosaniline, C 19 H 17 N 3 . — The formation of this sub- 
stance by oxidation of para-leucaniline and of a mixture of 
toluidine and aniline was mentioned above. The relation 
between para-rosaniline and para-leucaniline is probably ex- 
pressed by the following formulas : — 



fC 6 H 5 

a \ c 6 h 5 


fC 6 H 4 .NH 2 


fC 6 H 4 .NH 2 
C(OH) \ C 6 H 4 .NH 2 . 


ch| c 6 h 4 .nh 2 


IC 6 H 5 


[C 6 H 4 .NH 2 


IC 6 H 4 .NH 2 


M-phenyl- 


Para-leucaniline. 


Triamido-triphenyl-carbinol, 


methane. 




or Para-rosaniline. 



EOS ANILINE. 319 

Rosaniline, C 2 oH 2 iN 3 0. — This is the principal constituent 
of commercial fuchsine. It is formed by oxidizing a mixture of 
aniline and toluidine : — 

C 6 H 7 N + 2 C 7 H 9 N + 30 = C 20 H 21 N 3 O + 2 H 2 0. 

Experiment 77. In a dry test-tube put a little dry mercuric chlo- 
ride and a few drops of commercial aniline. Heat over a small name. 
Dissolve the product in alcohol, with the addition of a little hydro- 
chloric or acetic acid. The beautiful color of the solution is due to 
the presence of the hydrochloride or acetate of rosaniline. 

On the large scale, the oxidizing agent used is arsenic acid. 
Care is taken to remove all arsenic acid from the product, but 
it is nevertheless sometimes found in the products obtained in 
the market. Rosaniline crystallizes in needles or plates. It is 
very slightly soluble in water ; more readily soluble in alcohol. 
It forms three series of salts with monobasic acids. With hydro- 
chloric acid it forms the salts C 20 H 19 N 3 .HC1 and C 20 H 19 N 3 . 3 HCL 
The former is the substance known as fudisine, though some of 
the fuchsine met with in the market is the acetate of rosaniline, 
CsoHjgNg.GjE^Oa. The formation of the salts of rosaniline takes 
place as represented in the following equation : — 

fC 6 H 4 .NH 2 

C(OH)(C 6 H 4 .NH 2 ) 3 + HC1 = C j C 6 H 4 ,NH 2 . 

Para-rosaniline. I [ C 6 H 4 . NH . HC1 



Para-rosaniline hydrochloride. 

Fuchsine and the other salts of rosaniline dye wool and silk 
directly. For dyeing cotton cloth, however, a mordant is neces- 
sary. 

Dyeing. Animal fibres, in general, are colored directly by 
dyes ; that is to say, they have the power of forming with the 
dyes stable compounds which adhere to the fibres. This is not 
true of vegetable fibres, as cotton cloth and linen. Hence, in 
order to dye the latter, something must be added of such a 
character that, with the dye, it forms a compound which adheres 
to the fibres. Substances which act in this way are called 



320 DI-PHENYL-METHANE, ETC. 

mordants. Among the substances used as mordants are alu- 
minium acetate, ferric acetate, and some salts of tin. 

Experiment 78. Make a dilute solution of picric acid by dissolv- 
ing 2§ to 3? in 200 cc to 300 cc water. Iu a portion of it suspeud a few 
pieces of white yarn or flannel. The woollen material will be strongly 
dyed yellow. In another portion suspend a piece of ordinary cotton 
cloth. And in a third portion introduce a piece of cotton cloth which 
has been soaked in aluminium acetate and afterwards partly dried. 
The aluminium acetate can be made by treating a solution of sugar 
of lead with enough of a solution of alum to precipitate the lead, and 
then filteiing off the lead sulphate. The unprepared cotton cloth, 
when removed from the picric acid solution and washed, will be found 
to be only slightly colored; whereas, that piece which was soaked in 
the mordant will be found to be strongly dyed. Similar experiments 
may be made with fuchsine. 

Among the simpler aniline dyes are the following : — 

Hofmann's Violet. This is either the hydrochloric acid or 
acetic acid salt of tri-methyl-rosaniline. It is made b}' heating 
together a salt of rosaniline, methyl iodide, methyl alcohol, and 
caustic potash. 

Iodine Green is the iodide of penta-metlryl-rosaniline. 

Aniline Blue is tri-phenyl-rosaniline, C 2 oH 16 (C 6 H 5 ) 3 N3, which is 
formed by heating salts of rosaniline with an excess of aniline. 

Phthaleins. 

In speaking of phthalic anhydride, it was stated that when 
this substance is treated with phenols, phthalems are formed ; 
and, in speaking of resorcin, a markedly fluorescent body was 
mentioned as being formed when phthalic acid and resorcin are 
heated together. 

Phenol-phthalein, CooH^Oi. — This substance is formed by 
treating a mixture of phenol and phthalic anyhdride with sul- 
phuric acid or some other dehydrating agent : — 

2 C 6 H 6 + C 8 H 4 3 = CyB M 4 + H 2 0, 

Phenol. Phthalic Phenol- 

anhydride, phthale'in. 



PHTHALE1NS. 321 

The fused mass is dissolved in caustic soda, and the phenol- 
phthalein precipitated by the addition of an acid. It forms a 
granular crystalline powder. Its solution in alkalies is red or 
violet, according to the thickness of the la3'er. Acids destroy 
the color. Hence it is used as an indicator in alkalimetry as a 
substitute for litmus. 

Phenol-phthalem, like rosaniline, is a derivative of tri-phenyl- 
methane, as has been shown by the following somewhat compli- 
cated reactions : — 

The chloride of phthalic acid, or phthalyl chloride, C 8 H 4 2 C1 2 , 
when treated with benzene in the presence of aluminium chloride, 
gives up its two atoms of chlorine, and in their place takes up 
two phenyl groups, thus : — 

C 8 H 4 2 C1 2 -f 2 C 6 H 6 = C 8 H 4 2 (C 6 H 5 ) 2 + 2 HC1. 

Phthalyl chloride. Diphenyl-phthalide. 

The substance thus formed is known as diplienyl-plitlialide. 
Its conduct towards water and bases is such as to show that it 
is the anhydride of an acid : — 

C 8 H 4 2 (C 6 H 5 ) 2 -f H 2 = C 8 H 6 3 (C 6 H 5 ) 2 

or C 7 H 5 { C0 - 9H . 

1(C 6 H 5 ) 2 

When this acid is reduced by means of zinc dust it loses 
oxygen : — 

C ' H50 {(c% 2 = CA {(c% H 5 ) 2 +a 

And, finally, when the last product is distilled with baryta, it 
loses carbon dioxide and yields tri-phenyl-methane : — 

C 'M?r^ =Ch{cK + C0 2 . 

We have thus passed from phthalic anhydride to tri-phenyl- 



322 DI-PHENYL-METHANE, ETC. 

methane, and the reactions just referred to are in all probability 
correctly represented by the following formulas and equations : — 
C 6 H 5 r C 6 H 5 




^6*3.5 1 XT Q __ Q J ^6^5 

C 6 H 4 .CO 2 " I C 6 H 4 .C0 2 H. 

O 1 ^OH 

Dipbenyl-pbtbalide, or an- Tripbenyl-carbinol- 

hydride of tripbenyl-car- carbonic acid, 

binol-carbonic acid. 

{C 6 H 5 r C 6 H 5 

C 6 H 5 - C J ^ 6 ^ s + O. 

C 6 H 4 .C0 2 H " j C 6 H 4 .C0 2 H 

OH ^H 

Triphenyl-metbane- 
carbonic acid. 

C 6 H 5 
. C 6 H 5 co 
I C 6 H, 

H 

Tri-phenyl-metbane. 

Now, by making dinitro-diphenyl-phthalide, reducing it, and 
boiling the diazo compound with water, the product is phenol- 
phthalem. Hence, the latter compound appears to be the di- 
hydroxy derivative of diphenyl-phthalide : — 

C 6 H 4 .NH 2 rC 6 H 4 .OH 
q 1 C 6 H 4 .NH 2 q\ C 6 H 4 .OH 
C 6 H 4 .CO I C 6 H 4 .CO* 
O 1 lo 1 

Pbenol-phtbalein. 

The formula for phenol-phthalem may also be written thus : — 
C 6 H 4 .OH c C 6 H 4 co 
C 6 H 4 .OH^ ^O ' 

the curious arrangement of the carbonyl group being simply the 
sign of the anhydride condition between carboxyl and hydroxyl, 
of which the simplest expression is 

R< Uil = R< I + H 2 0. 
COOH CO 




FLUORESCEIN. 323 

Note for Student. — Although the reactions above briefly de- 
scribed may at first sight appear to be difficult to comprehend, they 
are in reality simple enough. The student is earnestly recommended 
not to slight them on account of the long names aud complex formulas 
involved. They afford an excellent example of the methods upon 
which we rely for determining the nature of complex substances. 
Notice that all appears dark until the well-known substance tri-phenyl- 
methane is obtained, which suggests that all the substances are deriva- 
tives of this fundamental hydrocarbon; and how easily, when this 
conception has once been formed, the interpretation of all the reactions 
follows. 

Among the other phthalems which deserve special mention is 
that which is formed with resorcin. 



Fluorescein, resorcin-phthalein, C 2 oHi 2 5 . — This beau- 
tiful substance is formed by simply heating together resorcin 
and phthalie anhydride : — 

2 C 6 H 4 (OH) 2 + C 8 H 4 3 = QaHjA -f 2 H 2 0. 

Its solutions in alkalies are wonderfully fluorescent. The sub- 
stance, which is sold under the name " uranin" for the purpose 
of exhibiting the phenomenon of fluorescence, is an alkaline salt 
of fluorescein. 

The reaction which takes place between resorcin and phthalie 
anhydride, when fluorescein is formed, is of the same kind as 
that which takes place between phenol and the anhydride to 
form phenol-phthalei'n. We should therefore expect to find that 
fluorescein has the formula — 



C< 



C 6 H 3 j OH 
6 3 iOH 

C 6 H 4 .CO 

10 J 



324 DI-PHENYL-METHANE, ETC. 

which shows its analogy to phenol-phthalein, 

C 6 H,.OH 



C 



C 6 H,.OH 
C 6 H 4 .CO 

O — ' 



It is found, however, that in reality fluorescein corresponds to 
the above formula less one molecule of water ; and it is believed 
that the water is given off as represented thus : — 

fC 6 H 3 {° H 

I C 6 H 3 ° 
C{ 3 lOH = Q»H U (V 

C 6 H 4 .CO 

o — ' 

Fluorescein. 

Eosin, tetra-brom-fluorescein, C2oH 8 Br 4 5 , is formed by 
treating fluorescein with bromine. Its dilute solutions have an 
exquisite, delicate pink color which suggests a color often seen 
in the sky at the dawn of day. Hence the name eosin, from 
<7ws, dawn. It is fluorescent, and is used as a dye. 



CHAPTER XVII. 
HYDROCARBONS, CnH 2n -s, AND DERIVATIVES. 

The hydrocarbons thus far considered are of three classes. 
They are : (1) paraffins, or saturated hydrocarbons of the 
marsh-gas series ; (2) unsaturated hydrocarbons related to 
the paraffins ; and (3) hydrocarbons which contain residues 
of the saturated paraffins and of benzene. 

We now pass to a brief consideration of a hydrocarbon which 
is made up of a residue of benzene and of an unsaturated par- 
affin. It bears to ethylene the same relation that toluene bears 
to marsh gas ; that is to say, it is phenyl-ethylene. 

Styrene, phenyl-ethylene, C 8 H 8 (= C 6 H 5 .CH.CH 2 ). — This 
hydrocarbon is contained in liquid storax, — a fragrant, hone}*- 
like substance which exudes from various plants, as the liquid- 
amber. It is formed by distilling cinnamic acid with lime : — 

C 9 H 8 2 = C 8 H 8 + C0 2 . 

Note for Student. — What does this reaction suggest with regard 
to the relation between cinnamic acid and styrene? 

It is also formed from phenyl -ethane, C 6 H 5 .C 2 H 5 , in the same 
way that ethylene is formed from ethane : — 

( C 2 H 6 + Br 2 = C 2 H 5 Br -f HBr 

I C 2 H 5 Br + KOH = C 2 H 4 + KBr -}- H 2 ' 

C 6 H 5 . C 2 H 5 -f- Br 2 = C 6 H 5 . C 2 H 4 Br + HBr ; 
C 6 H 5 .C 2 H 4 Br + KOH = C 6 H 5 .C 2 H 3 + KBr + H 2 0. 

Styrene. 



326 HYDROCARBONS, C n H 2n _ 8 , AND DERIVATIVES. 

Its formation by heating acetylene was mentioned on p. 

225 : . 

4 C 2 H 2 = C 8 H 8 . 

Note for Student. — What other polymeric product is obtained 
by heating acetylene ? 

Styrene is a liquid of an aromatic odor ; boils at 144° to 
144.5° ; insoluble in water; miscible with ether and alcohol in 
all proportions. 

When heated alone up to 300°, or even when allowed to stand 
at ordinary temperatures, it is converted into a polymeric modi- 
fication, called meta-styrene, which is a solid. This same change 
is readily effected by several reagents, such as iodine and con- 
centrated sulphuric acid. Styrene unites directly with chlorine 
and bromine in the same way that ethylene does (see p. 214) : — 

C 6 H 5 .C 2 H 3 + Br 2 = C 6 H 5 .C 2 H 3 Br 2 . 

Chromic acid and other oxidizing agents convert styrene into 
benzoic acid (see remarks, p. 248). Some higher members of 
this series have been prepared, such as phenyl-propylene, phenyl- 
butylene, etc.; but at present they are not of sufficient import- 
ance to make their consideration necessary. 

Styrene is closely related to cinnamic acid, from which the 
interesting and important compounds of the indigo group are 
obtained. 

Styryl alcohol, C 9 H 10 O(= C 6 H 5 .CH.CH .CH 2 OH). — This 

alcohol occurs in nature in the form of an ethereal salt of cin- 
namic acid in liquid storax, and also in balsam of Peru. It 
forms long, thin needles, which melt at 33°. It boils at 
250°. It takes up hydrogen, and yields phenyl-propyl alcohol, 
C 6 H 5 .CH 2 .CH 2 .CH 2 OH (see p. 283) : — 

C 6 H 5 .CH.CH.CH 2 OH + H 2 = C 6 H 5 .CH 2 .CH 2 .CH 2 OH. 

By treatment with hydriodic acid it yields allyl-benzene 
(phenyl-propylene), C 6 H 5 .CH.CH.CH 3 , and toluene. 



CINNAMIC ACID. 327 

When oxidized with platinum black it is converted into the 
corresponding aldehyde, cinnamic aldehyde ; and, by further 
oxidation, into cinnamic acid. The relations between the three 
substances are the familiar ones of a primary alcohol, and the 
corresponding aldehyde and acid : — 

C 6 H 5 .CH .CH .CH 2 OH. C 6 H 5 .CH .CH .CHO. 

Styryl alcohol. Cinnamic aldehyde, 

CeH3.CH.CH.CO2H. 

Cinnamic acid. 

These compounds are simply the phenyl derivatives of allyl 
alcohol, acrolein, and acrylic acid : — 

CH 2 .CH .CH 2 OH. CH 2 .CH .CHO. CH 2 .CH .C0 2 H. 

Allyl alcohol. Acrolein or Acrylic acid. 

acrylic aldehyde. 

Cinnamic acid, , ^^ ^ CH CH eQ ^ ) 

Pnenyl-acrylic acid, > 
Cinnamic acid is found in liquid storax, partly in the free con- 
dition, and partly in the form of an ethereal salt in combination 
with styryl alcohol, as styryl cinnamate, in the balsams of Tolu 
and Peru. It can be made synthetically : — 

1 . By heating together benzoic aldehyde and acetyl chloride : — 

C 6 H 5 .COH + CH 3 .COCl = C 6 H 5 .C 2 H 2 .C0 2 H + HC1. 

This reaction will be better understood by writing it in two 
equations : — 

(1) C 6 H 5 .CH!Oi + C!iSiH.COCl= C 6 H 5 .CH.CH.C0C1 + H 2 0; 

Cinnamyl chloride. 

(2) C 6 H 5 .CH .CH .COC1 + H 2 = C 6 H 5 .CH .CH .C0 2 H + HC1. 

Cinnamyl chloride. 

The kind of action represented in equation (1) is not un- 
common. We have already met with it in the formation of 
mesitylene from acetone (see p. 250) , in which case two hydro- 
gens from each of three methyl groups unite with an oxygen 



328 HYDROCARBONS, C n H 2n _ 8 , AND DERIVATIVES. 

atom from each of the three carbonyl groups. The product 
is called a condensation-product, and the action is known as 
condensation. 

2. By heating together benzoic aldehyde and acetic anhy- 
dride : — 

C 6 H 5 .COH + (C 2 H 3 0) 2 = C 6 H 5 .C 2 H 2 .C0 2 H + C 2 H 4 2 . 

It is probable that the action between benzoic aldehyde and 
acetic anhydride is of the same kind as that between the alde- 
hyde and acetyl chloride. 

3. By treating benzal chloride with sodium acetate : — 

C 6 H 5 .CH!~cf 2 j +_CJH]H.C0 2 Na = C 6 H 5 .CH.CH.C0 2 Na + 2HC1. 
CfrHs.CH.CH.CO^a + HC1 = C 6 H 5 .CH.CH.C0 2 H + NaCl. 

The acid is now manufactured on the large scale by the last 
method. 

Cinnamic acid is a solid which crystallizes in monoclinic 
prisms. It melts at 133°, and boils at 300° to 304°. It is 
easily decomposed into styrene and carbon dioxide : — 

C 6 H 5 .CH.CH.C0 2 H = C 6 H 5 .CH.CH 2 + C0 2 . 

Oxidizing agents convert it first into benzoic aldehyde and 
then into benzoic acid. Nascent hydrogen converts it into 
hydro-cinnamic or phenyl-propionic acid, C 6 H 5 .CH 2 .CH 2 ,C0 2 H 
(p. 295). It unites with hydrochloric, hydrobromic, and hydri- 
odic acids : — 

GglLj . O2H2 • CO2H -f- HOI = O6H5.Cy2H3Ol.CO2H. 

Phenyl-chlor-propionic 
acid. 

Treated with substituting agents, such as nitric acid, etc., it 
yields substitution-products in which the entering atoms or 
groups are contained in the benzene residue, in the ortho and 
para positions relatively to the acrylic acid residue, C 2 H 2 .C0 2 H. 
Bromine yields the addition-product C 6 H5.C 2 H 2 Br2.C0 2 H. 



COUMARIN. 329 

( C* TT CO TT 
Nitro-cinnamic acids, C 6 H 4 { 2 2 ' 2 . — The ortho- 

and para-acids are formed by dissolving cinnamic acid in nitric 
acid. 

Note for Student. — What are the products when toluene is 
treated with nitric acid? When benzoic acid is treated in the same 
way? To which case is the above analogous? 

Amido-cinnamic acids, 6 H 4 { N Vr 2 ' 2 • — These acids 

are formed by treating the nitro-acids with reducing agents. 
The ortho-acid loses water when set free from its salts, and 

forms the anhydride carbostyril, C 6 H 4 < 2 2 ^ C.OH, analogous 

to hydro-carbostyril (p. 296). 

Ooumarin, C 9 H 6 o/ = C 6 H, { p 2 ** 2 ? ], is a compound found 

in Tonka beans, and in some other plant-substances. It has 
been made synthetically from salicylic aldehyde and acetic anhy- 
dride, just as cinnamic acid is made from benzoic aldehyde and 

acetic anhydride. The first product of this action is probably 

Cp tr POO TT 
ortho-hydroxy-cinnamic acid, or coumaric acid, C 6 H 4 < * 2 " , 

l. Orl(°) 

which then loses water, yielding the anhydride or coumarin. 
Coumarin has a pleasant odor, like that of vanillin, and is used 
for flavoring. Treated with bases, it yields salts of coumaric 
acid. 



CHAPTER XVIII. 
PHBNYL-ACBTYLBNE AND DERIVATIVES. 

Phenyl-acetylene, acetenyl-benzene, C 6 H 5 .C.OH, bears 
to acetylene the same relation that styrene, or phenyl-ethylene, 
bears to ethylene. It is made from styrene in the same wa}^ 
that acetylene is made from ethylene : — 

(1) C 2 H 4 + Br 2 = C 2 H 4 Br 2J 

(2) C 2 H 4 Br 2 + 2 KOH = C 2 H 2 + 2 KBr + 2 H 2 0. 

C 6 H 5 .C 2 H 3 + Br 2 = C 6 H 5 .C 2 H 3 Br 2 ; 
C 6 H 5 .C 2 H 3 Br 2 + 2 KOH = C 6 H 5 .C 2 H + 2 KBr + 2 H 2 0. 

Phenyl-acetylene. 

It is a liquid which boils at 139° to 140°. It unites directly with 
four atoms of bromine, forms metallic derivatives, and, in gen- 
eral, conducts itself like acetylene (which see) . 

Phenyl-propiolic acid, C 9 H 6 2 (= 6 H 3 .C.C.CO 2 H).— This 
acid is a carbox}! derivative of phenyl-acetylene, bearing to it 
the same relation that cirmamic acid bears to phenyl-ethylene. 
It is made from cinnamic acid, by treating brom-cinnamic acid, 
C 6 H 5 . C 2 HBr . C0 2 H, with alcoholic potash : — 

C 6 H 5 .C 2 HBr.C0 2 H = C 6 H 5 .C 2 .C0 2 H + HBr. 

It forms long needles, which melt at 136° to 137°. When 
heated with water, it breaks up into carbon dioxide and 
phenyl-acetylene . 

Ortho-nitro-phenyl-propiolio acid, GbHW-kJq 2 , is 

made from ortho-nitro-cinnamic acid, in the same way that 
phenyl-propiolic acid is made from cinnamic acid (see pre- 



INDIGO AND ALLIED COMPOUNDS. 331 

ceding paragraph). It is of special interest, for the reason 
that it can easily be transformed into indigo. The trans- 
formation is most readily effected by boiling it with alkalies 
and grape sugar, or some other mild reducing-agent. The 
reaction is represented by the following equation : — 

2 C 6 H 4 j ^1°^ + H 4 = C 16 H 10 N 2 O 2 + 2 C0 2 + 2 H 2 0. 

CiNOglo) indigo. 

Ortho-nitro-phenyl- 
propiolic acid. 

The acid is at present manufactured on the large scale, for 
the purpose of making indigo. 



Indigo and Allied Cojipounds. 

In several plants, Indigo/era tinctoria, Isatis tinctoria, etc., 
there occurs a glucoside called indican, which, under the influ- 
ence of dilute mineral acids and certain ferments, breaks up, 
yielding indigo-blue and a substance resembling the glucoses. 
The indigo of commerce is prepared in the East and West 
Indies, in South America, Egypt, and other warm countries. 
At the proper stage the plants are cut off down to the ground, 
put in a large tank, and covered with water. Fermentation 
takes place, the indican breaking up and yielding iudigo, as 
above stated. The liquid becomes green, and then blue. 
When the fermentation is finished, the liquid is drawn off 
into a second tank. This liquid contains the coloring-matter 
in solution. In contact with the air it is oxidized, forming 
indigo, which, being insoluble, is thrown down. In order to 
facilitate the precipitation of the indigo, the liquid is thoroughly 
stirred. Finally, the liquid is drawn off, the precipitated indigo 
pressed and dried, and then sent into the market. 

The substance prepared as above has a dark-blue color, and 
contains other coloring-matters besides indigo-blue. Its value 
depends upon the amount of the definite compound, indigo-blue, 
which it contains. 



332 PHENYL- ACETYLENE AND DERIVATIVES. 

Indigo-blue, indigotin, C 16 H 10 N 2 O 2 . — Indigo-blue is ob- 
tained from commercial indigo by reducing it to indigo-white, 
and then exposing the clear colorless solution to the air, when 
indigo : blue is precipitated. 

Experiment 79. Into a test-tube put a small quantity of powdered 
indigo ; add flue zinc filings or zinc dust and caustic soda. When the 
mixture is heated the indigo forms a colorless solution. When this 
result has been reached, pour some of the solution into a small evapo- 
rating-dish. Contact with the air colors it blue. 

Indigo-blue can be made artificially by a number of methods, 
among which the two following are the principal ones : — 

1. By boiling ortho-nitro-phenyl-propiolic acid (which see) 
with an alkali and grape sugar : — 

2 C 6 H 4 i S 2 A C ° 2H + 4 H = C 16 H 10 N 2 O 2 + 2 H 2 + 2 C0 2 . 

I JNU 2 (o) 

2. By heating isatine (which see) with phosphorus trichlo- 
ride, phosphorus and acetyl chloride. 

Without going into the mechanism of these reactions, we see 
that there are two general ways of obtaining indigo artificially. 
The first starts from cinnamic acid, which is successively con- 
verted into ortho-nitro-cinnamic acid and ortho-nitro-phenyl- 
propiolic acid ; the second starts from benzoic acid, which is 
converted into ortho-nitro- and ortho-amido-benzoic acids. The 
latter is then converted successively into the chloride, cyanide, 
and corresponding acid, the anhydride of which is isatine. For 
fuller details of the reactions involved in the formation of ortho- 
nitro-phenyl-propiolic acid, see p. 330 ; and for similar details 
in regard to isatine, see p. 291. As has been stated, indigo is 
now manufactured on the large scale by the first of the two 
methods above given. 

Indigo-blue crystallizes from aniline in dark-blue crystals. 
It sublimes in rhombic crystals. Its vapor has a purple-red 
color. It is insoluble in water, alcohol, and ether ; soluble in 
aniline and chloroform. Oxidizing agents convert it into isa- 



INDIGO-WHITE. 333 

tine (which see). Heated with solid caustic potash, it yields 
carbon dioxide and aniline ; boiled with a solution of caustic 
potash and finery-powdered black oxide of manganese, it is 
converted into ortho-amido-benzoic acid (anthranilic acid) (see 
p. 291). 

A great many compounds related to indigo have been made 
incidentally to the study of its chemical conduct. The syn- 
thesis of indigo has been effected, as a result of this study. 
The work undertaken was suggested bj- the fundamental facts, 
above mentioned, that indigo when decomposed, readily yields 
aniline and ortho-amido-benzoic acid. The question which 
investigators have endeavored to answer is, What relations do 
indigo-blue and the compounds allied to it bear to ortho-amido- 
benzoic acid? Although, as far as indigo-blue is concerned, 
this has proved to be a difficult question, to which a final 
answer is still lacking, as far as some of the simpler derivatives 
are concerned it has been answered. Two of these, oxindol 
and isatine, have been treated in connection with the simpler 
compounds, to which they are most closely related. A few 
others will here be mentioned. 

Indigo-white, C 16 H 12 N 2 02, is formed by reduction of indigo- 
blue, as above described. Its solutions rapidly turn blue in the 
air, in consequence of the formation of indigo-blue. 

When indigo is oxidized with nitric acid, isatine, C 8 H 5 N0 2 , 
is formed : — qjj^^ + q 2 = 2 C 8 H 5 M) 2 . 

When isatine is treated with sodium amalgam, it takes up 
hydrogen, and yields dioxindol, C 8 H 7 N0 2 : — 

C 8 H 5 N0 2 + H 2 = C 8 H 7 N0 2 . 

Isatine. Dioxindol. 

By further reduction, dioxindol loses an atom of oxygen, yield- 
ing oxindol, C 8 H 7 NO : — 

C 8 H 7 N0 2 + H 2 = C s H 7 NO + H 2 0. 

Dioxindol. OxindoL 



334 PHENYL- ACETYLENE AND DERIVATIVES. 

The relations between oxindol and isatine cannot readily be 
made clear without a careful study of some very complex re- 
actions. 

It would also lead too far and be uu profitable to discuss here 
the constitution of iodigo-blue itself. Suffice it to say, that 
it has been shown to consist of a doubled group very similar 
to that of oxindol. 



CHAPTER XIX. 

HYDROCARBONS CONTAINING TWO BENZENE 
RESIDUES IN DIRECT COMBINATION. 

Just as the marsh-gas residue, methyl, CH 3 , unites with methyl 
CH 3 
to form ethane, I , so the beuzene residue, phenyl, C 6 H 5 , 
CH 3 rH 

unites with phenyl to form the hydrocarbon, diphenyl, I , and 

C 6 H 5 

similar residues of toluene, and the higher members of the series 
unite in a similar way to form homologues of diphenyl. 

Diphenyl, C 12 H 10 (= C 6 H 5 .C 6 H 5 ). — This hydrocarbon is made 
by treating brom-benzene with sodium : — 

2 C 6 H 5 Br + 2 Na = C 12 H 10 + 2 NaBr ; 

and by conducting benzene through a tube heated to redness : — 

2 C 6 H 6 = C^Hjo -f- H 2 . 

It forms large, lustrous plates. It melts at 70.5°, and boils 
at 254°. It is easily soluble in hot alcohol and ether. 

Diphenyl is an extremely stable substance. It resists the 

action of ordinary oxidizing agents, but with strong ones it 

yields benzoic acid. A large number of derivatives of diphenyl 

have been studied. A curious one, known as carbazol, occurs 

in coal tar. This has been shown to be a substituted ammonia 

containing a residue of diphenyl. It is properly designated by 

the name diphenyl-imide, and is represented by the formula 

C 6 H 4 

I >NH. It has been made synthetically by passing the vapor 

of diphenyl amine, NH \ (i 5 , through a red-hot tube, a reaction 
1 C 6 H 5 



336 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

taking place which is analogous to that mentioned above as 
taking place when benzene is treated in the same way, the 
product in the latter case being diphenyl. 

Naphthalene, C 10 H S . — While the relations of diphenyl to 
benzene are clearly shown by its simple synthesis from brom- 
benzene, the relations of naphthalene to benzene have been 
discovered through a careful study of its chemical conduct. 
The facts can be best interpreted by assuming that the molecule 
of naphthalene is formed by the union of two benzene residues 
in such a way that they have two carbon atoms in common, as 
represented in the formulas 



HC-CH-C-CH-CH 

i i t 




H H 

HC X XT X CH 

i i i 


1 1 1 
HC-CH-C-CH-CH 


and 


1 1 1 
HC v / C \ / Cxi 



H H 

How this conception was reached will be shown below, after 
the properties and the reactions of naphthalene shall have been 
discussed. 

Naphthalene is a frequent product of the heating of organic 
substances. Thus, it is formed by passing the vapors of alco- 
hol, ether, acetic acid, volatile oils, petroleum, benzene, toluene, 
etc., through red-hot tubes ; and, also, by treating ethylene and 
acetylene in the same way. It is therefore found in coal tar, 
and is sometimes found in gas-pipes used for gas made by 
heating naphtha, gasoline, etc., to high temperatures. It has 
been made synthetically by conducting phenyl-butylene bromide 
over highly -heated lime : — 

C 6 H 5 .C 4 H 7 Br 2 = C 4 H 4 .C 2 .C 4 H 4 + H 2 + 2HBr; 

and by conducting isobutyl-benzene over lead oxide : — 

C 6 H 5 .C 4 H 9 + 3 = C 4 H 4 .C 2 .C 4 H 4 + 3 H 2 0. 

Neither of these reactions, however, is of much assistance 



NAPHTHALENE. 337 

in enabling us to form a conception in regard to the nature of 
naphthalene. 

Naphthalene is prepared on the large scale from those por- 
tions of coal tar which boil between 180° to 220°. This material 
is treated with caustic soda, and then with sulphuric acid, and 
distilled with water vapor. 

It forms colorless, lustrous, monoclinic plates. It melts at 
79.2°, and boils at 216.6°. It has a pleasant odor; is volatile 
with water vapor, and sublimes readily. It is insoluble in water; 
easily soluble in boiling alcohol, from which it can be crystal- 
lized. Oxidizing agents convert it into phthalic acid (see 
Exp. 74). 

The ease with which naphthalene yields phthalic acid, sug- 
gests that the hydrocarbon is probably a di-derivative of benzene 
containing two hydrocarbon residues ; such, for example, as is 

represented by the formula C^ ] 2 2 . Such a substance, how- 

( v_,.,H 2 

ever, contains unsaturated paraffin residues, and hence ought 
readily to take up bromine, hydrobromic acid, etc. Bromine 
and chlorine are indeed taken up easily, but the products thus 
obtained act rather like the addition-products of benzene than 
the addition-products of the unsaturated paraffins. They break 
up readily, and yield stable substitution-products of naphtha- 
lene ; and, further, the first product of the action of bromine 
on naphthalene is not an addition-product, but mono-brom- 
naphthalene, C 10 H 7 Br, a fact which shows that substitution takes 
place more easily with naphthalene than addition. ^Ve have 
seen that a hydrocarbon containing a benzene residue and an 
unsaturated paraffin residue, as, for example, styrene or phenyl- 
ethylene. C G H 5 .C 2 H 3 , and phenyl-acetylene, C 6 H5.C 2 H, when 
treated with bromine or hydrobromic acid, takes them up as 
readily as ethylene and acetylene, and this action takes place 
before substitution. According to this, naphthalene ought to 
take up bromine with avidity before substitution of its hydrogen 
takes place. 



338 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

The formula C 6 H 4 -J 2 2 and similar ones being thus rendered 
^ O2H2 

extremely improbable, the next thought that suggests itself is 
that the two groups C 2 H 2 may be united, as represented in the 

(CH.CH 
formula C 6 H, ) I . Assuming, further, that the two groups 

(CH.CH 

are united to two carbon atoms of the benzene residue which 
are in the ortho relation to each other, we may write this same 
formula thus : — 

H 

HC X X C-CH-CH 

I I I 

HC X C-CH-CH 

H 

or, what is the same thing, — 



HC 


H 


H 

1 


CH 

1 


HC 


H 


c 

H 


CH 



This formula represents naphthalene as made up of two 
benzene residues united in such a way that the}^ have two 
carbon atoms in common. This, as has been stated, repre- 
sents the hypothesis at present held in regard to the nature of 
naphthalene. 

As regards the assumption that the two residues are united 
through carbon atoms which are in the ortho position relatively 
to each other, it should be said that this assumption is made 
because phthalic acid is the product of oxidation ; and the facts 
already considered have shown us that terephthalic acid must 
be represented by the formula 



NAPHTHALENE. 339 

C0 2 H 

I I 

HC X /CH 

x cr 

C0 2 H 



and isophthalic acid by 

C0 2 H 

HCT X CH 

I I 

HC N /CC0 2 H 

X C / 
H 

and hence, in terms of the accepted hypothesis, the third pos- 
sible formula must be given to phthalic acid ; viz., — 

H 

HC X x C.C0 2 H 

I I 

HC X /C.C0 2 H 

H 

Are there any facts besides those above mentioned which 
make the hypothesis appear probable ? 

By a different line of reasoning, based upon other facts, the 
conclusion is reached that naphthalene is made up of two ben- 
zene residues which have two carbon atoms in common, and the 
only formula which represents this conception is the one already 
given. The facts which lead to this conclusion are the fol- 
lowing : — 

When nitro-naphthalene is oxidized it yields nitro-phthalic 
acid. This shows that the nitro group is contained in a 
benzene residue ; and we may represent it by the formula 



340 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

( C H 
CfrH 3 .NO a ] 2 2 , the oxidation taking place as indicated thus :— • 

C 6 H 3 . N0 2 { p h + 9 ° = C6Hs • N ° 2 { CO H + H *° + 2 C °s- 

By reducing this same nitro-naphthalene, amido-naphthalene 
is obtained ; and, when this is oxidized, phthalic acid is 
formed : — 

C 6 H 4 j OP ' NH * + 12 O = C 6 H 4 1 ™& + 2 C0 2 +HN0 3 +H 2 0. 

These two reactions show (1) that the part of nitro-naphtha- 
lene in which the nitro group is situated is a benzene residue ; 
(2) that there is another benzene residue in the compound into 
which the nitro group has not entered. 

It has been noticed, also, that by oxidation of a naphthalene- 
sulphonic acid, both sulpho-phthalic and phthalic acid itself are 
obtained. 

It follows, from these facts, that naphthalene is made up of 
two benzene residues, and the only way in which a hydrocarbon 
of the formula C 10 H 8 can be thus made up, is by having two 
carbon atoms common to the two residues, as represented in 
the formula alread} r given. It cannot be made up thus : — 



nor thus : — 



/"I 


H 


HC 7 X CH 

1 1 


X CH 

1 


HC X /C\ 
H 


/CH 

NT 
H 


HC X X CH 

1 i 


H 

X CH 

1 


HC V y CH 

X C X 


CH 

C X 
H 



for neither of these formulas expresses the fundamental idea of 



DERIVATIVES OF NAPHTHALENE. 341 

the presence of two benzene residues in the same molecule. 
The only formula which expresses this idea in terms of the 
commonly accepted hypothesis for benzene is 

H H 

KC / X C X X CH 



HC \ / C \ / CH 

x cr x cr 

H H 

The proof just given for this formula is independent of any 
notions regarding the ortho, meta, and para relations in 
benzene. As phthalic acid is the product of oxidation, it 
follows that the carboxyl groups in the acid must bear to each 
other the relation expressed by the formula 

H 

HC X x C-C0 2 H 

I I 

HC V /C-C0 2 H 

X CT 
H 

and, therefore, that in all ortho compounds the substituting 
groups bear this same relation to each other. Hence, by start- 
ing with the notion that the above formula represents phthalic 
acid, — and to this notion, it must be remembered, we are led 
independently of any facts connected with the formation of the 
acid from naphthalene, — the accepted formula of naphthalene 
follows naturally. And, on the other hand, we are led, by a 
study of naphthalene itself, to the accepted formula, and from 
this the above formula for phthalic acid follows. 

Derivatives of Naphthalene. 

An interesting fact which has been discovered by a study of 
the mono-substitution products of naphthalene is this, — that 
two, and only two, varieties are known. There is an a- and 



342 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

a /?-chlor-naphthalene, an a- and a /?-brom-naphthalene, etc., 
etc. This fact is quite in harmony with the views held 
regarding the constitution of naphthalene, as will readily be 
seen b} r examining the formula somewhat more in detail. 
We see that there are two, and only two, kinds of relations 
which the hydrogen atoms bear to the molecule ; all those 
marked with an a being of one kind, and all those marked 
with a /3 being of another kind : — 

aH aH 

0HC 7 X C / X CH/3 

I I I 

/?H(\ /C x /CH/3 

N c c 

aH aH 

Here, again, a problem presents itself like that which was 
considered in connection with the di-substitution products of 
benzene. Our theory gave us three formulas, and three com- 
pounds are known. The problem was, to determine which 
formula to assign to each compound. Here we have two 
formulas for two brom-naphthalenes and other mono-substi- 
tution products of naphthalene, and we actually have two 
compounds ; and the question arises, which of the two 
formulas must we assign to a given compound? The 
method adopted is simple, and can be explained in a few 
words. That nitro derivative of naphthalene which is known 
as a-nitro-naphthalene yields nitro -phthalic acid by oxida- 
tion ; and the relation of the nitro group to the carboxyl 
groups, in this acid, has been determined. It is expressed 

by the formula 
J N0 2 

HC X x C-C0 2 H 

I I 

HC X /C-C0 2 H 

cr 

H 

Formula I. 



NAPHTHOL. 343 

while the formula of the other nitro-phthalic acid is 

H 

N0 2 C / X C-C0 2 H 
I I 

HC X /C-C0 2 H 

x cr 

H 

Formula II. 

As a-nitro-naphthaleiie yields the acid of formula I., it fol- 
lows that in it the nitro group must occupy the position of one 
of the lrydrogen atoms marked a in the above formula for naph- 
thalene. Those substitution-products of naphthalene which 
belong to the same series as a-nitro-naphthalene are called a 
derivatives. In the ft compounds the substituting group or 
atom must occupy the place of one of the hydrogen atoms 
marked j3. 

Among the derivatives of naphthalene are the following : — 



Naphthoic acid, Ci H 7 .CO 2 H, which bears to naphthalene 
the same relation that benzoic acid bears to benzene. 

a-Naphthol, Ci H 7 .OH. — This compound is made from naph- 
thalene in the same way that phenol is made from benzene : — 

1. By treating a-naphthyl- amine, C 10 H 7 .NH 2 , with nitrous 
acid. 

Note for Student. — Write the equations. 

2. By melting a-naphthalene-sulphonic acid with caustic 
potash. 

Note for Student. — Write the equation. 

a-Naphthol is a solid which melts at 96°. It has an odor 
somewhat resembling that of phenol. Its general chemical 
conduct is much like that of phenol. Toward oxidizing 
agents, however, its action is peculiar. Thus, when boiled 



344 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

with potassium chlorate and hydrochloric acid, a di- chlorine 
substitution-product is formed ; and at the same time a 
second oxygen atom enters, and the product has the char- 
acteristics of the quinones (which see). It is di-chlor- 
naphtho-quinone. It will be remembered that ordinary 
quinone is formed by the oxidation of hydro-quinone, a di- 
hydroxyl derivative. 

Some of the substitution-products of naphthol are used as 
dyes ; as, for example, clinitro-naphiJioL C 10 H 5 (NO 2 ) 2 OH, 
which is known as Martius's Yellow; dinitro-naplithol- 
sidphonic acid, C 10 H 4 (NO 2 ) 2 (SO 3 H).OH, the potassium salt 
of which, K 2 C 10 H 4 N 2 SO 8 , is known as Ncqohthol Yellow S. 
With diazo compounds, naphthol has a remarkable power of 
combination ; and a great many derivatives containing resi- 
dues of diazo compounds, and of naphthol or its substitution- 
products, have been made, and some of them have found 
application as dyes. The simplest compound of this kind is 
formed by bringing together naphthol and diazo-benzene 
nitrate : — 
C 10 H 7 .OH + C 6 H 5 -N 2 -N0 3 = C 10 H C j ^ C ^ 5 + HN0 3 . 

It is called naphtliol-diazo-benzene. The dye known as Poir- 
rier's Orange II. is a sulphonic acid of naphthol-diazo-benzene, 
and is probably formed by treating diazo-benzene-sulphonic acid 
with naphthol. 

Naphtho-quinone, C 10 H 6 O 2 . — This compound is obtained 
by oxidizing naphthalene with chromic acid ; also by oxidiz- 
ing a-amido-a-naphthol and other di-substitution products of 
naphthalene in which the two substituting groups are in the 
para position relatively to each other. It bears to naphthalene 
the same relation that ordinary quinone bears to benzene ; that 
is, it is naphthalene in which two hydrogen atoms are replaced 
by two oxygen atoms. 

It forms yellow needles, which melt at 125°. Like ordinary 



QUINOLINE AND ANALOGOUS COMPOUNDS. 345 

quinone, it is volatile with water vapor. Hydriodic acid con- 
verts it into hydro -naphtho-quinone : — 

Ci H 6 O 2 + H 2 = C 10 H 6 (OH) 2 . 

Note for Student. — Compare with the action of reducing agents 
on ordinary quinone. 

Di-hydroxy-naphtho-quinone, CioH 4 |L , is a dye 

known by the name naphthazarin, on account of its resem- 
blance to alizarin (which see) . 

Two homologues of naphthalene — methyl- and ethyl-naph- 
thalene — have been prepared. /3-Methyl-naphthalene has been 
found in coal tar. 



QuiNOLINE AND ANALOGOUS COMPOUNDS. 

It has been stated, that, by distilling quinine and cinchonine 
with caustic potash, pyridine and some of its homologues are 
obtained. At the same time a base belonging to another series 
is formed, together with some of its homologues. This base is 
known as quinoline, to suggest its formation from quinine. It 
has the composition expressed by the formula C 9 H 7 N. It occurs 
in coal-tar, where an isomeric compound, called isoquinoline, is 
also found. Among compounds homologous with quiuoline are 
the following : — 

Quinaldine, a-Methyl-quinoline . . . C 10 H 9 N. 
Lepidine, y-Methyl-quinoline .... C 10 H 9 N. 
Cryptidine C U H U N. 



Quinoline, C 9 H 7 N. — Quinoline is formed by the distillation 
of quinine, cinchonine, or strychnine, with caustic potash. It 
is formed from certain derivatives of benzene. 



346 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

1 . By passing allyl-aniline over heated lead-oxide : — 

C 6 H 5 .NH.C 3 H 5 = C 9 H 7 N + 4H. 

2. By heating together glycerin, aniline, and nitro-benzene : — 

(1) C 6 H 5 .M) 2 + C 3 H 8 3 = C 9 H 7 N + 3H 2 0+0 2 ; 

(2) C 6 H 5 NH 2 + C 3 H 8 3 = CAN + 3 H 2 + H 2 ; 

(3) 2 C 6 H 5 NH 2 + C 6 H 5 N0 2 + 3C 3 H 8 3 = ZCJS^N + 11 H 2 0. 

3. From di-chlor-qninoline : — 

C 9 H 5 C1 2 N + 4 H = C 9 H 7 N + 2 HC1. 

The last method is the most suggestive, as it leads to a defi- 
nite view in regard to the relation between quinoline and ben- 
zene. Di-chlor-quinoline is made by treating hydro-carbostyril 
with phosphorus pentachloride. Hydro-carbostyril is the anhy- 
dride of ortho-amido-hydro-cinnamic acid. This relation is 
partly expressed by the formula : — 



H 

1 


H 2 

C X X CH 

i i 


HC , 
X C 


1 1 
C CO 



H H 

The transformation of hydro-carbostyril into di-chlor-quino- 
line takes place easily ; and the reaction can be best interpreted 
by assuming quinoline to be made up thus : — 

H H 

HC / X C X X CH 

I I I 
HC X /C\ /CH 
N CT X N X 
H 

Quinoline is thus regarded as formed from the union of a 



QUINOLINE. 347 

residue of benzene and a residue of pyridine, in the same way 
that naphthalene is believed to be formed from two residues of 
benzene. The formula suggests the existence of two isomeric 
quinolines, in one of which the nitrogen is in the a position, as 
represented in the above formula, while in the other it is in 
the /? position. Ordinary quinoline belongs to the a series ; 
while isoquinoline belongs to the j3 series. 

Quinoline is a liquid which boils at 237°. Potassium perman- 
ganate converts it partially into cinchomeronic acid, C 7 H 5 N0 4 . 
This is a pyridine-dicarbonic acid, C 5 H 3 N(C0 2 H) 2 . The for- 
mation of this acid is analogous to that of phthalic acid from 
naphthalene. 

Quinoline readily takes up hydrogen, forming hydro-qitinoline, 
C 9 H 9 N, and tetra-hydro-quinoline, C 9 H n N. These, as well as 
the hydrogen addition-products of pyridine, are believed to exist 
in the alkaloids. Tetra-hydro-quinoline has been found in the 
crude quinoline obtained by distilling cinchonine with caustic 
soda. 

Many derivatives of quinoline have been made. Substitution- 
products are obtained by treating nitro-products of substituted 
benzene with glycerin and aniline. 

A sulphonic acid is obtained by treatment of quinoline with 
sulphuric acid. From this, hydroxy-quinoline, C 9 H (OH)N, has 
been obtained. Hydroxy-quinoline, like quinoline itself, takes up 
hydrogen, forming tetra-liydro-liydroxy-qninoline, C 9 H 10 .OH.N. 
Finally, by treating this compound with methyl iodide, methyl 
is introduced, and a product obtained which is called hydro- 
methoxy '-quinoline : — 

C 9 H n ON + CH 3 I = C 10 H 13 NO + HI. 

This substance resembles quinine, and its hydrochloric acid 
salt is used in medicine to some extent as a substitute for 
quinine . The salt is known as kairine. 



CHAPTER XX. 

HYDROCARBONS CONTAINING TWO BENZENE 
RESIDUES INDIRECTLY COMBINED. 

Diphenyl and naphthalene have been shown to consist of two 
benzene residues in direct combination. Diphenyl-methane is 
an example of a hydrocarbon consisting of two benzene resi- 
dues in indirect combination, C 6 H 5 . CH 2 . C 6 H 5 . As diphenyl- 
methane is closely related to toluene, it was treated of in 
connection with the hydrocarbons of the benzene series. 
There are some hydrocarbons which have been shown to 
consist of two benzene residues united by means of resi- 
dues of unsaturated paraffins. The most important of these 
is the well-known anthracene. , 

Anthracene, C u Hi . — Anthracene is formed under condi- 
tions similar to those which give rise to the formation of 
naphthalene, especially by heating organic substances to a 
high temperature, and is hence found in coal tar. 

It has been made synthetically from benzene derivatives 
by a number of methods : — 

1. By passing benzyl-toluene, C 6 H 5 . CH 2 . C 6 H 4 . CH 3 , over 
heated lead oxide : — 

C 14 H 14 + 20 = C 14 H 10 + 2 H 2 0. 

2. By heating benzyl-phenol with phosphorus pentoxide : — 
2C 6 H 5 .CH 2 .C 6 H 4 (OH) = C 14 H 10 + C 6 H 6 + C 6 H 5 (OH) + H 2 0. 

3. By heating ortho-brom-benzji bromide with sodium : — 

2 C 6 H 4 j CB - 2Br + 4Na= C 14 H 10 + 4 NaBr + 2 H ; 
(. Br(o) 



ANTHRACENE. 349 

= C 6 H 4 1 ™ } C 6 H 4 + 4 NaBr -f- 2 H. 

Anthracene is prepared in large quantity from those portions 
of coal tar which boil between 340° and 360°. The distillate 
is redistilled, and that which remains in the retort after the 
temperature has reached 350° is crystallized from xylene. It 
is then crystallized from alcohol, and finally sublimed. It is 
difficult to get it in perfectly pure condition. The color can 
be removed by dissolving the substance in benzene, and expos- 
ing it to direct sunlight. It forms laminae, or monoclinic plates, 
which are fluorescent. It melts at 213°, and boils above 360°. 

Anthracene takes up hydrogen, forming di-hyclro-antJiracene, 
C^H^, and Jiexa-hydro- anthracene, C 14 H 16 . It takes up bromine 
and chlorine, forming first addition-products, and then substi- 
tution-products. 

Oxidizing agents convert anthracene into anihra-quinone, 
C 14 H 8 2 , just as they convert naphthalene into naphtha- 
quinone. 

The formation of anthracene from ortho-brom -benzyl-bro- 
mide (see above) furnishes strong proof in favor of the view 
that anthracene consists of two groups, C 6 H 4 , united by the 
group C 2 H 2 ; thus, C 6 H 4 . C 2 H 2 . C 6 H 4 . It hence appears as a 
diphenylene 1 derivative of ethane, C 2 H 2 (C 6 H 4 ) 2 , analogous to 
diphenyl-ethane, C 2 H 4 (C 6 H 5 ) 2 . This conception may also be 
expressed thus : — 



H 

HC / X C- 

i i 


-CH- 

1 


H 

-C x X CH 

i i 


1 1 
HC X >C- 

H 


-CH- 


1 1 
H 



This is the formula commonly accepted for anthracene. It is 

1 Phenylene = CeH 4 . 



350 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

in harmony with a large number of facts, and has been an 
efficient aid in investigations on anthracene and its derivatives. 

Anthraquinone, C 14 H 8 2 ( = C 6 H 4 < co > C 6 H 4 j . — Anthra- 

quinone is formed by direct oxidation of anthracene : — 

Ci 4 H 10 + 3 = C 14 H 8 2 + H 2 0. 

The simplest synthesis of anthraquinone that has been ef- 
fected consists in distilling calcium phthalate. It is believed 
that the reaction which takes place is analogous to that which 
takes place when the calcium salt of a monobasic acid is distilled. 
As is well known, in the latter case a ketone containing one 
carbonyl group is formed ; and it is believed that the product 
formed in the distillation of calcium phthalate contains two 
carbonyl groups, and that it is a representative of a class of 
bodies which may be called diketones. The subject of diketones 
was briefly discussed under the head of Quinones (which see) . 
The equation representing the formation of anthraquinone from 
calcium phthalate is here given : — 

C 6 H 4 {£0°>Cai 

'---"--; = c ^ < co > C « H * + 2 CaC °3- 

<WS£> Ca j 

i._ * 

Experiment 80. Dissolve 5S commercial anthracene in 220 cc hot 
glacial acetic acid. Slowly add to the boiling solution 50s chromic acid 
in 50 cc acetic acid (50 p. c). Boil for some hours. After cooling, add 
750 cc water ; filter ; wash ; dry ; and sublime. 

Anthraquinone forms rhombic crystals. It sublimes in yellow 
needles ; is insoluble in water, but slightly soluble in alcohol 
and ether. It is an extremely stable compound, resisting the 
action of alcoholic potash and oxidizing agents. Melted with 
solid potassium hydroxide, it yields benzoic acid : — - 

C 14 H 8 2 + 2 KOH = 2 C 7 H 5 2 K ; 

C 6 H 4 < ££ > Oft -I- 2 KOH = 2 C 6 H 5 .COOK. 



ALIZARIN. 351 

Reducing agents convert it successively into oxanthranol, 
C 14 H 10 O 2 , anthranol, C 14 H 10 O, and anthracene, C^H^. These 
changes may be represented thus : — 

Cft<™>Cft + H 2 = C«H 4 <^ OH >>C c H 4 ; 

Oxanthranol. 

C ^ < ^ ( ° H) > C <&* + H 2 = C 6 H 4 < i >C 6 H 4 + H 2 0; 

CO CH 

Anthranol. 

&&*< ^i° H) > C « H 4 + H 2 = C 6 H 4 < | >C 6 H 4 + H 2 0. 
(H CH 

When heated with zinc dust, it yields anthracene. A great 
many derivatives of anthraquinone have been made. Among 
the best known are the hydroxyl derivatives, some of which 
are much-prized dyes which are manufactured in great quan- 
tities. 

The hydroxyl derivatives of anthraquinone can be made by 
melting either the bromine derivatives or the sulphonic acids 
with caustic potash. 

Alizarin, 'i 

Di-hydroxy-anthraquinone, i CuH8aC= C "H 6 2 (OH) 2 ]. 

Alizarin is the well-known dye which is obtained from madder 
root. The substance found in the root is ruberythric acid, a 
glucoside of the formula C^H^Ou. When this is treated with 
dilute acids or alkalies or ferments, it is decomposed, yielding 
alizarin and a glucose : — 

Q20H22O11 = C 14 H 8 4 + CeH^Otf ■+■ H 2 0. 

Alizarin. Grlucose. 

It is formed by melting dichlor- or dibrom-anthraquinone or 
anthraquinone-monosulphonic acid with caustic potash : — 

C 14 H 7 2 .S0 3 K + KOH + O = C 14 H 6 2 (OH) 2 + K 2 S0 3 . 

Alizarin is now manufactured from anthracene on the large scale, 



352 HYDROCARBONS WITH TWO BENZENE RESIDUES. 

and large tracts of land which were formerly used for culti- 
vating madder are now used for other purposes. 

Experiment 81. Dissolve 20& anthraquinone in a small quan- 
tity of fuming sulphuric acid, heating gradually to 260°. Dissolve 
the product in a litre of water. Neutralize with finely-powdered 
chalk; filter. Precipitate with a solution of sodium carbonate; 
fi 1+ er; and finally evaporate to dryness. The salt thus obtained is 
impure sodium anthraquinone-mono-sulphonate. In an iron crucible 
mix 10s of the sulphonate, 40s sodium hydroxide, and 3s potassium 
chlorate, and heat for several hours at 165° to 175°. The formation 
of alizarin, during the melting, is shown by the dark-purple color of 
the mass. When a little of this is dissolved in water, it should form 
a beautiful purple-red solution. Continue the melting until the mass 
acts in this way. Dissolve the mass in f 1 to l 1 water, and acidify. 
Alizarin is thrown down in brown amorphous flakes. Filter off, dry, 
and sublime between watch-glasses. 

Alizarin forms red needles, which melt at 275° to 277°. It 
dissolves in alkalies, forming dark purple-red solutions. When 
heated with zinc dust, it yields anthracene. It was this reaction 
which gave the first clue to the nature of alizarin, and led, soon 
after, to its synthesis. 

Some compounds, isomeric with alizarin, and also derived 
from anthracene, are known. 

^TT' «. • |0„H 8 6 = [0 11 H 5 2 (0H)J. 

Tri-hydroxy-anthraqumone, > 

Purpurin is contained in madder root, and is therefore found 
in madder alizarin. It can be made by melting alizarin-sul- 
phonic acid with caustic potash, and also by melting tri-brom- 
anthraquinone with caustic potash. 

Anthrapurpurin, isopurpurin, C u H 5 2 (OH) 3 , is found in 
artificial alizarin. 



Phenanthrene, O u H 10 , which is isomeric with anthracene, is 
also found in the higher boiling parts of coal tar. The chemical 



PHENANTHRENE. 353 

conduct of this hydrocarbon has led to the conclusion that it 
consists of two benzene residues directly united, as in diphenyl, 
C 6 H 5 — C 6 H 5 ; and that a further connection between the benzene 
residues is established through a group — CH = CH — , thus 
giving as the expression of the structure the formula 

^6^4 — C G H 4 

I I . 

CH = CH 



CHAPTER XXI. 

GLUCOSIDES, ALKALOIDS, ETC. -CONCLUSION. 

Under the head of the sugars, reference was made (see p. 
180) to a class of bodies called glucosides, which occur in 
nature in the vegetable kingdom. These bodies break up 
under the influence of dilute acids or ferments into sugar and 
other bodies. Thus, salicin breaks up, according to the equa- 

tion C 6 H 4 (OH) CH 2 (OC 6 H u 5 ) + H 2 

= C 6 H 12 6 + C 6 H 4 (OH)CH 2 OH 

Dextrose. Salicylic alcohol. 

into dextrose and salicylic alcohol, the alcohol corresponding 
to salicylic acid. Some of the more important glucosides are 
mentioned below. 

Aesculin, C 15 H 16 9 + 1£ H 2 0, occurs in the bark of the 
horse-chestnut tree (Aesculus Hippocastanum) . It breaks up 
into dextrose and aesculetin : — 

Ci 5 H 16 9 + H 2 == CgH^Og -f- C 9 H 6 4 . 

Aesculin. Dextrose. Aesculetin. 

Its water solution shows blue fluorescence. 

Amygdalin, C20H97NO11 4- 3 H 2 0, occurs particularly in bit- 
ter almonds ; also, in the kernels of apples, pears, peaches, 
plums, cherries, etc. With emulsin, which is an aqueous 
extract of almonds, amygdalin is broken up in benzoic alde- 
hyde, hydrocj^anic acid, and dextrose : — 

C^H^NOu + 2 H 2 = G 7 H 6 + CNH + 2 C^Og. 

Tannins. — Under this head are included a large number of 
substances, some of which are glucosides. They all give either 



SALICIN. 355 

a blue or a green color with ferric salts. They have a bitter, 
astringent taste ; are precipitated by solutions of gelatin ; pre- 
cipitate solutions of metals, and absorb oxygen in alkaline 
solution. They also unite with animal membranes, forming 
compounds which resist the putrefactive forces, thus tanning 
them, or converting them into leather. Reference has already 
been made to gallo-tannic acid, which breaks up into gallic acid 
and glucose. 

Helicin, C 13 H 16 7 + f H 2 0, is formed by the oxidation of 
salicin (which see) . It has also been made artificially by mix- 
ing an alcoholic solution of acetochlorhydrose with the potassium 
compound of salicylic aldehyde : — 

C 6 H 7 C10 5 (C 2 H 3 0) 4 + C 7 H 5 2 K + 4 C 2 H 6 
= C 13 H 16 7 + KC1 + 4C 2 H 5 .C 2 H 3 2 . 

Acetochlorhydrose is formed by heating dextrose with an 
excess of acet}! chloride. 

Helicin breaks up into dextrose and salicylic aldehyde. 

Indican, C 26 H 31 N0 17 , occurs in woad. It yields, among 
other products, dextrose and indigo blue : — 

C 26 H 31 N0 17 + 2 H 2 = 3 C 6 H 10 O 6 + C 8 H 5 NO. 

Indigo blue. 

Myronic acid, C 10 H 1 yNS 2 1 o, is found in the form of the 
potassium salt in black mustard seed. When treated with 
myrosin, which is contained in the aqueous extract of white 
mustard seed, potassium myronate is converted into dextrose, 
allyl mustard oil, and acid potassium sulphate : , — ■ 

C 10 H 18 NS 2 O 10 K = QHjA + C 3 H 5 .NCS + KHS0 4 . 

Salicin, C I3 Hi80 7 , occurs in willow bark, and in the bark and 
leaves of poplars. Its decomposition into salicylic alcohol and 
dextrose has been referred to (see preceding page) . 



356 ALKALOIDS. 

Saponin, C s Jl- oi Oi S , is found in soap root {Saponaria offici- 
nalis) . Its water solution forms a lather like that formed by 
soap. It is said that this is utilized for the purpose of giving 
to ' ' soda water " the appearance of effervescence. 

Alkaloids. 

The alkaloids are compounds occurring in plants, frequently 
constituting those parts of the plants which are most active 
when taken into the animal body. They are hence sometimes 
called the active principles of the plants. Many of these sub- 
stances are used in medicine. As regards their chemical char- 
acter, they are basic in the sense that ammonia is basic ; they 
contain nitrogen, and form salts, just as ammonia does, i.e., by 
direct addition to the acids. These and other facts lead to the 
belief that the alkaloids are related to ammonia — that they are 
substituted ammonias. Recently it has been shown that several 
of the alkaloids are related to pyridine (see p. 309) and quino- 
line (see p. 345) . Only a few of the more important alkaloids 
need be mentioned here. 

Alkaloids of Peruvian Bark. 

Quinine, C 2c H 24 N 2 2 + 3 H 2 0. — This valuable substance is 
obtained from the outer bark of the Cinchona varieties. YvTien 
oxidized, it yields derivatives of pyridine. In view of the 
interest connected with quinine, the discovery of its relation to 
pyridine and quinoline has led to a large number of investiga- 
tions on the derivatives of these two bases, and it is probable 
that before long it will be possible to make quinine synthetically 
in the laboratory. 

The salts of quinine are formed by direct addition of the base 
to the acids. Thus, we have 

Quinine hydrochloride . C20H24N2O2 . HC1 ; 
Quinine nitrate .... C20H24N2O2 . HN0 3 ; 
Quinine sulphate . . . C20H24N2O2 . H 2 S0 4 , etc.. etc. 



PIPERINE. 357 

Cinchonine, C 19 H 22 N 2 0, cinchonidine, Ci 9 H 22 N 2 0, and 
other bases occur with quinine in Peruvian bark. 

Cocaine, Ci T H 21 N0 4 , is found in cocoa leaves (Erythroxylon 
coca) . Very little is known regarding its chemical nature. Its 
hydrochloric acid salt, C 17 H 21 N0 4 .HC1, has recently come into 
prominence in medicine, owing to the fact that it is a powerful 
anaesthetic. 

Nicotine, C 10 H U N 2 , occurs in tobacco leaves in combination 
with malic acid. Potassium permanganate converts it into 
nicotinic acid, which is one of the possible pyridine-monocar- 
bonic acids. 

Alkaloids of Opium. 

Opium is the evaporated sap which flows from incisions in 
the capsules of the white poppy (Papaver somniferum), before 
they are ripe. The two principal alkaloids contained in opium 
are morphine and narcotine. 

Morphine, Ci 7 H 19 N0 3 + H 2 0, is a crystallizable solid which 
is difficultly soluble in water, alcohol, and ether. When de- 
composed, it yields pyridine, trimethyl- amine, and phenanthrene, 
together with other products. 

Narcotine, C 22 H 23 N0 7 , has been shown to contain three 
methyl groups, which are split off, as methyl chloride, when 
the substance is heated with hydrochloric acid. 

Piperine, C 17 H 19 N0 3 , is contained in black pepper. When 
treated with alcoholic potash, it breaks up into piperidine and 
piperic acid : — 

C 17 H 19 N0 3 + H 2 - C 5 H U N + C 12 H 10 O 4 . 

Piperidine. Piperic acid. 



358 CONCLUSION. 

Piperidine, C 5 H n N, which, as just stated, is formed by the 
decomposition of piperine, has been made synthetically by treat- 
ing pyridine with nascent hydrogen : — 

C 5 H 5 N + 6H = C 5 H U N. 

Pyridine. Piperidine. 

It ma} r therefore be called hexa-hydropyridine (see p. 309) . 

Strychnine, C 21 H 22 N 2 2 , and brucine, C 23 H 26 N 2 4 + 4 H 2 0, 

are two alkaloids which occur in nux vomica. 



In the animal body occur a large number of complicated sub- 
stances, the study of which, at this stage, would hardly be 
profitable. Thus, there are the albumins, caseins, and fibrin ; 
the coloring-matters of the blood, oxyhemoglobin, haemoglobin, 
etc. It may be said that, notwithstanding the importance of 
these substances, our knowledge of their chemistry is quite 
limited. 

The study of the composition of animal substances, such 
as milk, urine, etc., and of the relations of the chemical sub- 
stances occurring in the body to the processes of life, is the 
object of physiological chemistry. Without a good knowledge 
of the general chemistry of the compounds of carbon, however, 
the subjects treated under the head of Physiological Chemistry 
cannot be understood. 



INDEX. 



A. 
Acetamide, 197. 
Acetates, 59. 
Acetic acid, 57. 
Acetic aldehyde, 46. 
Acetic anhydride, 61. 
Acetone, 70. 
Acetophenone, 307. 
Acetyl chloride, 61. 
Acetylene, 224. 
Acid, Acetic, 57. 

Aconitic, 223. 

Acrylic, 220. 

Adipic, 142. 

Alpha-toluic, 294. 

Amido-acetic, 194. 

Amido-benzoic, 291. 

Amido-caproic, 196. 

Amido-cinnamic, 329. 

Amido-formic, 193. 

Amido-isethionic, 196. 

Amido-succinic, 197. 

Angelic, 220. 

Anisic, 305. 

Aspartic, 197. 

Azelaic, 142. 

Barbituric, 206. 

Behenic, 130. 

Benzoic, 285. 

Brassylic, 142. 

Brom-propionic, 131. 

Butyric, 132. 

Capric, 129. 

Caproic, 129. 

Caprylic, 129, 



Acid, Carbamic, 191. 
Carbolic, 271. 
Carbonic, 156. 
Cerotic, 130. 
Chlor-acetic, 63. 
Chlor-propionic, 131. 
Cimic, 220. 
Cinnamic, 327. 
Citraconic, 223. 
Citric, 174. 
Crotonic, 221. 
Cyan-acetic, 141. 
Cyanic, 83. 
Cyanuric, 84. 
Dibrom-succinic, 172. 
Di-chlor-acetic, 63. 
Erucic, 220. 
Ethylene-lactic, 163. 
Ethylidene-lactic, 161. 
Fermentation lactic, 

38. 
Formic, 54. 
Fulminic, 102. 
Fumaric, 222. 
Gallic, 306. 
Glyceric, 166. 
Glycocholic, 158. 
Glycolic, 158. 
Glyoxylic, 170. 
Heptoic, 129. 
Hippuric, 293. 
Hydracrylic, 162. 
Hydro-cinnamic, 295. 
Hydrocyanic, 80. 
Hydrosorbic, 220. 
Hydroxy-succinic, 167. 



Acid, Hyenic, 130. 
Hypogseic, 220. 
Isethionic, 165. 
Isobutyric, 133. 
Isophthalic, 298. 
Isosuccinic, 146. 
Itaconic, 223. 
Lactic, 160. 
Laurie, 130. 
Leinoleic, 229. 
Male'ic, 222. 
Malic, 167. 
Malonic, 142, 144. 
Margaric, 130. 
Melissic, 130. 
Mellitic, 299. 
Mesaconic, 223. 
Mesitylenic, 295. 
Mesoxalic, 170. 
Mucic, 176. 
Myristic, 130. 
Naphthoic, 343. 
Nitro-benzoic, 290. 
Nitro-cinnamic, 329. 
Nitro-phenyl - propio- 

lic, 330. 
Nonoic, 129. 
Octoic, 129. 
Ole'ic, 221. 
Oxalic, 142. 
Oxaluric, 206. 
Oxybenzoic, 304. 
Palmitic, 134. 
Parabanic, 205. 
Para-oxybenzoic, 304. 
Pelargonic, 129. 



360 



INDEX. 



Acid, Phenyl-acetic, 294. 

PheDyl-propiolic, 330. 

Phthalic, 297. 

Picric, 274. 

Pimelic, 142. 

Piperic, 357. 

Propiolic, 228. 

Propionic, 131. 

Protocatechuic, 305. 

Prussic, 80. 

Pyrogallic, 279. 

Pyrotartaric, 142, 147. 

Racemic, 172. 

Roccellic, 142. 

Saccharic, 176. 

Salicylic, 300. 

Sarcolactic, 161. 

Sebacic, 142. 

Sorbic, 228. 

Stearic, 134. 

Styphnic, 278. 

Suberic, 142. 

Succinic, 142, 144. 

Sulpho-cyanic, 84. 

Tannic, 306. 

Tartaric, 171. 

Tartronic, 167. 

Taurocholic, 196. 

Teracrylic, 220. 

Terephthalic, 298. 

Tetrolic, 228. 

Toluic, 294. 

Tri-carballylic, 152. 

Tri-chlor-acetic, 63. 

Trimesitic, 248. 

Uric, 207. 

Uvitic, 248. 

Vanillic, 306. 

Valeric, 133. 
Aconitic acid, 223. 
Acrolein, 218. 
Acrylic acid, 220. 

aldehyde, 218. 
Adipic acid, 142. 
Aesculin, 354. 
Alcohols, 34, 



Alcohols, Di-acid, 136. 

Hex-acid, 153. 

Primary, 122. ' 

Secondary, 121. 

Tertiary, 124. 

Tetr-acid, 152. 

Tri-acid, 147. 
Aldehyde ammonia, 48. 
Aldehydes, 46, 128. 
Alizarin, 351. 
Alkaloids, 356. 
Allanto'in, 207. 
Alloxan, 207. 
Allyl alcohol, 216. 

isosulpho-cyanate , 
217. 

mustard oil, 217. 

sulphide, 217. 
Alpha-toluic acid, 294. • 
Amido-acetic acid, 194. 
Amido-acids, 192. 
Amido-benzene, 262. 
Amido-benzoic acids, 291. 
Amido - cinnamic acids, 

329. 
Amido-formic acid, 193. 
Amido-toluenes, 263. 
Amygdalin, 354. 
Amyl alcohols, 126. 
Amylene, 213. 
Angelic acid, 220. 
Aniline, 262. 

dyes, 317. 
Anisic acid, 305. 
Anthracene, 348. 
Anthranilic acid, 291. 
Anthrapurpurin, 352. 
Anthraquinone, 350. 
Anthraquinone-sulphonic 

acids, 351. 
Arabinoses, 178. 
Arabite, 152. 
Arachidic acid, 130. 
Arsenic-methyl com- 
pounds, 104. 
Asparagine, 200, 



Aspartic acid, 197. 
Azelaic acid, 142. 



Barbituric acid, 206. 
Behenic acid, 130. 
Benzal chloride, 258. 
Benzaldehyde, 283. 
Benzene, 233. 

Dinitro, 261. 

Hexa-chlor, 255. 

hexachloride, 256. 
Benzene-sulphonic acid, 

268. 
Benzine, 110. 
Benzoic acid, 285. 

Amido-, 291. 

Hydroxy-, 300. 

aldehyde, 283. 
Benzophenone, 307. 
Benzoyl chloride, 289. 
Benzyl alcohol, 281. 

cyanide, 289. 
Bitter-almond oil, 283. 
Biuret, 204. 
Boiling-point, 8. 
Borneo camphor, 313. 
Borneol, 313. 
Brassylic acid, 142. 
Br om-e thane, 29. 
Brom-methane, 27. 
Bromoform, 28. 
Brom-propionic acid, 131. 
Brucine, 358. 
Butane, 20, 108, 114. 
Butter, 151. 
Butyl alcohols, 123. 
Butylene, 213. 
Butyric acid, 132. 



Cacodyl, 103. 

compounds, 104. 
Caffeine, 208. 
Camphor, 313. 

Artificial, 313, 



INDEX. 



361 



Cane sugar, 184. 
Capric acid, 129. 
Caproic acid, 129. 
Caprylic acid, 129. 
Caramel, 185. 
Carbamic acid, 193. 
Carbamide, 202. 
Carbamines, 88. 
Carbobydrates, 177. 
Carbolic acid, 271. 
Casein, 358. 
Cellulose, 187. 
Cerotic acid, 130. 
Chlor-acetic acid, 63. 
Chloral, 53. 

hydrate, 53. 
Chlor-ethane, 29. 
Chlorhydrin, 149. 
Chlor-m ethane, 27 
Chloroform, 28. 
Chlor-propionic acid, 131. 
Cholic acid, 196. 
Cimicic acid, 220. 
Cinchouidine, 357. 
Cinchonine, 357. 
Cinnamic acid, 327. 

Amido-, 329. 

Nitro-, 329. 
Citric acid, 174. 
Coal tar, 232. 
Cocaine, 357. 
Collidine, 309. 
Coumarin, 329. 
Creatine, 201. 
Creatinine, 202. 
Cresols, 276. 
Crotonic acid, 221. 
Cuminic aldehyde, 285. 
Cuminic aldehyde, 285. 
Cuminol, 285. 
Cuminyl alcohol, 283. 
Cyan-acetic acid, 141. 
Cyan-amides, 201. 
Cyanates, 90. 
Cyanic acid, 83. 
Cyanides, 86. 



Cyanogen, 79. 

chlorides, 83. 
Cyanuric acid, 84. 
Cymene, 252. 
Cymogene, 110. 



Dextrin, 191. 

Dextrose, 179. 

Di-acetamide, 199. 

Diazo-benzene com- 
pounds, 264. 

Di-brom-benzene, 256. 

Di-chlor-acetic acid, 63. 

Dichlorhydrin, 149. 

Di-cyan-diamide, 201. 

Di-methyl-amine, 95. 

Di-methyl-benzene, 243. 

Di-methyl-carbinol, 127. 

Di-methjd-ethyl-methane, 
116. 

Di-methyl-ketone, 70. 

Di-m ethyl -phosphine, 103. 

Di-methyl-xanthine, 208. 

Dinitro-benzene, 261. 

Dioxindol, 333. 

Diphenyl, 335. 

Di-phenyl-methane, 315. 

Diphenyl ether, 273. 

Dipropargyl, 229. 

Dodecane, 108. 

Dulcite, 154. 

Durene, 233. 

Dynamite, 151. 

E. 
Eosin, 324. 
Erucic acid, 220. 
Erythrite, 152. 
Erythrose, 178. 
Ethane, 20, 24. 
Ether, 42. 
Ethereal salts, 66. 
Ethers, Formation of, 41. 
Ethers, Compound, 66. 
Mixed, 45. 



Ethyl acetate, 68. 

alcohol, 37. 
Ethyl aldehyde, 46. 

bromide, 29. 

carbamine, 88. 

carbinol, 127. 

chloride, 29. 

cyanide, 86. 
Ethylene, 213. 

chloride, 32. 

cyanide, 145. 

glycol, 136. 

lactic acid, 164. 
Ethyl ether, 42. 
Ethylidene chloride, 32, 

50. 
Ethyl iodide, 29. 

isocyanide, 88. 

isosulphocyanate, 92. 

mercaptan, 74. 

methyl ether, 45. 

mustard oil, 92. 

nitrate, 68. 

phosphate, 68. 

phosphoric acid, 68. 

sulphate, 68. 

sulphuric acid, 42, 68. 



Fats, 151. 
Fatty acids, 129. 
Fehliug's solution, 181. 
Fermentation, 38. 

Alcoholic, 38. 

Lactic acid, 38. 
Ferments, 38. 
Ferricyanogen com- 
pounds, 82. 
Ferrocyanogen com- 
pounds, 81. 
Flashing-point, 110. 
Fluorescein, 323. 
Formic acid, 54. 

aldehyde, 46. 
Formida, constitutional, 
15. 



362 



INDEX. 



Formula, Determination 

of, 12. 
Fructose, 182. 
Fruit sugar, 182. 
Fuclisine, 319. 
Fulminates, 102. 
Fulminic acid, 102. 
Fumaric acid, 222. 

G. 

Galactose, 184. 
Gallic acid, 304. 
Gasoline, 110. 
Glucose, 179. 
Glucosides, 351. 
Glyceric acid, 166. 
Glycerin, 147. 
Glycerose, 178. 
Glycine, 158, 194. 
Glycocholic acid, 158. 
Glycocoll, 194. 
Gly colic acid, 158. 
Glycols, 136. 
Glyoxylic acid, 170. 
Grape sugar, 179. 
Guanidine, 201. 
Guanine, 208. 
Gums, 191. 
Gun cotton, 188. 

H. 

Hecdecane, 108. 
Helicin, 355. 
Heptanes, 108. 
Heptyl alcohols, 128. 
Heptoic acid, 129. 
Hexanes, 20, 108, 116. 
Hexyl alcohols, 128. 
Hexylene, 213. 
Hippuric acid, 293. 
Homology, 20, 108. 
Hydracrylic acid, 162. 
Hydrazines, 99. 
Hydro-carbostyril, 296. 
Hydro-cinnamic acid, 295. 
Hydrocyanic acid, 80. 



Hydroquinone, 278. 
Hydrosorbic acid, 220. 
Hydroxy fatty acids, 155. 
Hydroxy succinic acids, 

167. 
Hyenic acid, 130. 
Hypogseic acid, 220. 



Indican, 355. 
Indigo, 331. 
Indigo-blue, 332. 
Indigo-white, 333. 
Inversion, 185. 
Invert sugar, 185. 
Iodo-ethane, 29. 
Iodo-methane, 27. 
Iodoform, 28. 
Isatine, 291. 
Isethionic acid, 165. 
Isobutane, 114. 
Isobutyl alcohol, 124. 
Isobutyric acid, 133. 
Isocyanates, 90. 
Isocyanides, 88. 
Isohexane, 117. 
Isomerism, 31. 

Physical, 163. 
Isonitroso compounds, 

101. 
Isopentane, 116. 
Isophthalic acid, 298. 
Isopropyl alcohol, 120. 
Isopurpurin, 352. 
Isosuccinic acid, 146. 
Iso-sulpho-cyantes, 91. 
Itaconic acid, 223. 

K. 

Kairine, 347. 
Kerosene, 110. 
Ketones, 70. 

L. 

Lactic acids, 160. 
Lactose, 186. 



Laurie acid, 130. 
Laurinol, 313. 
Leucine, 196. 
Levulose, 182. 
Lutidine, 309. 

M. 
Male'ic acid, 222. 
Malic acid, 167. 
Malonic acid, 142, 144. 
Malonyl urea, 206. 
Maltose, 187. 
Mannite, 153. 
Mannose, 184. 
Margaric acid, 130. 
Marsh gas, 20, 23. 
Melissic acid, 130. 
Mellitic acid, 299. 
Melting-points, 8. 
Mercaptans, 74. 
Mercury ethyl, 105. 

fulminate, 102. 
Mesaconic acid, 223. 
Mesitylene, 248. 
Mesitylenic acid, 295. 
Mesoxalic acid, 170. 
Metaldehyde, 49. 
Metamerism, 31. 
Methane, 20, 23. 
Methyl alcohol, 34. 

aldehyde, 46. 

amine, 94. 

bromide, 27. 

chloride, 27. 

cyanide, 86. 

iodide, 27. 
Methyl-phenyl ether, 273. 
Methyl-phosphine, 103. 
Methyl-phosphinic acid, 

103. 
Methyl-sulphuric acid, 68. 
Methylene iodide, 27. 
Milk sugar, 186. 
Morphine, 357. 
Mucic acid, 176. 
Mustard-oils, 91. 



INDEX. 



363 



Myronic acid, 355. 
My rosin, 355. 

N. 
Naphtha, 110. 
Naphthalene, 336. 
Naphthols, 343. 
Naphthoquinone, 346. 
Narcotine, 357. 
Nicotine, 311, 357. 
Nitriles, 87. 
Nitro-benzene, 260. 
Nitro-benzoic acids, 290. 
Nitro-cellulose, 188. 
Nitro-chloroform, 101. 
Nitro-cinnamic acids, 329. 
Nitroform, 101. 
Nitrogen, Estimation, 11. 
Nitro-glycerin, 151. 
Nitro-methane, 100. 
Nitroso-compounds, 101. 
Nitro-toluenes, 261. 
Nonane, 108. 



Octane, 108. 
Octyl alcohol, 128. 
Oils, Drying, 229. 
Olefiant gas, 213. 
Oleic acid, 221. 
Olein, 151. 
Opium bases, 357. 
Orcein, 279. 
Orcin, 279. 
Oxalates, 144. 
Oxalic acid, 142. 
Oxaluric acid, 206. 
Oxalyl urea, 205. 
Oximes, 101. 
Oxindol, 295. 
Oxybenzoic acid, 304. 



Palmitic acid, 134. 
Palmitin, 151. 
Paper, 189. 



Parabanic acid, 205. 
Para-cyanogen, 80. 
Paraffin, 110. 
Paraffins, 108. 
Paraldehyde, 49. 
Para - oxybenzoic acid, 

304. 
Para-rosaniline, 318. 
Pentanes, 20, 108, 116. 
Pentyl alcohols, 125. 
Perseite, 154. 
Petroleum, 109. 
Phenanthrene, 352. 
Phenol, 271. 

Nitro, 274. 

phthale'in, 320. 

Tri-nitro, 274. 
Phenyl acetate, 273. 
Phenylacetic acid, 294. 
Phenyl -acetylene, 330. 
Phenyl-acrylic acid. 327. 
Phenyl-amine, 262. 
Phenyl-ethyl alcohol, 283. 
Phenyl-mercaptan, 275. 
Phenyl-propyl alcohol, 

283. 
Phosphines, 103. 
Phthaleins, 320. 
Phthalic acid, 296. 

anhydride, 297. 
Picoline, 309. 
Picric acid, 274. 
Pimelic acid, 142. 
Piperic acid, 357. 
Piperidine, 311, 358. 
Piperine, 357. 
Polymerism, 31. 
Primary alcohols, 122. 
Propane, 20. 
Propargyl alcohol, 227. 
Propionic acid, 130. 
Propyl alcohol, 120. 
Propylene, 213. 
Protocatechuic acid, 305. 
Prussic acid , 80. 
Pseudocumene, 251. 



Purpurin, 352. 
Pyridine, 309, 311, 358. 
Pyrocatechin, 277. 
Pyrogallic acid, 279. 
Pyrogallol, 279. 
Py rotartaric acid , 142 , 147. 
Pyroxylin, 188. 

Q. 

Quinaldine, 345. 
Quinine, 356. 
Quinoline, 345. 
Quinone, 308. 

R. 

Racemic acid, 172. 
Resorcin, 277. 
Resorcin-phthale'in, 323. 
Rhamnose, 179. 
Rhigolene, 110. 
Roccellic acid, 142. 
Rosaniline, 319. 

S. 
Saccharic acid, 176. 
Salicin, 355. 
Salicylic acid, 300. 
Salicylic aldehyde, 302. 
Salicylid, 304. 
Saponification, 69. 
Saponin, 356. 
Sarcosine, 195. 
Sebacic acid, 142. 
Secondary alcohols, 121. 
Soaps, 135. 
Sodium ethyl, 104. 
Sorbic acid, 228. 
Sorbite, 154. 
Starch, 189. 
Stearic acid, 134. 
Stearin, 151. 
Strychnine, 358. 
Styphnic acid, 278. 
Styrene, 325. 
Styryl alcohol, 326. 
Suberic acid, 142. 



364 



INDEX. 



Substitution, 26. 
Succinic acid, 142, 144. 

anhydride, 146. 
Sugar of milk, 186. 
Sulpho-cyanic acid, 84. 
Sulpho-cyanates, 91. 
Sulphonic acids, 76. 
Sulpho-urea, 206. 
Sulphur ethers, 75. 



Tannic acid, 306. 
Tannin, 306, 354. 
Tartaric acid, 171. 
Tartronic acid, 167. 
Taurine, 196. 
Taurocholic acid, 196. 
Terebenthene, 312. 
Terephthalic acid, 298. 
Terpenes, 311. 
Tertiary alcohols, 124. 
Tertiary butyl alcohol, 

124. 
Tetra-chlor-methane, 28. 
Tetra - methyl - methane, 

116. 



The'ine, 208. 
Theobromine, 208. 
Thymol, 278. 
Tolu balsam, 242. 
Toluene, 242. 

Amido, 263. 

Nitro, 261. 
Toluic acids, 294. 
Toluidines, 263. 
Tolyl carbinol, 283. 
Tri-acetamide, 199. 
Tri-brom-phenol, 274. 
Tri-carballylic acid, 152. 
Tri-chlor-acetic acid, 63. 
Trichlorhydrin, 149. 
Trimesitic acid, 248. 
Tri-methyl-amine, 96. 
Tri-methyl-carbinol, 127. 
Tri-methyl-phosphine, 

103. 
Tri-methyl-xanthine, 208. 
Tri-nitro-m ethane, 104. 
Tri-nitro-phenol, 274. 
Tri-nitro-resorcin, 278. 
Tri-phenyl-methane, 316. 
Turpentine, 312. 



U. 

Unsaturated compounds 

210. 
Urea, 202. 
Uric acid, 207. 
Uvitic acid, 248. 

V. 

Valeric acids, 133. 
Valylene, 229. 
Vanillic acid, 306. 
Vanillin, 306. 

W. 
Wood spirits, 34. 

X. 

Xanthine, 207. 
Xanthogenic acid, 157. 
Xylenes, 243. 
Xylidines, 264. 
Xylite, 152. 
Xylose, 179. 

Z. 
Zinc ethyl, 104. 



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International Law. 



THE great revival of the study of political science in America makes a 
new work on' International Law almost a necessity. The subject grows 
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their mutual intercourse, and every question that arises between them adds 
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ing, in 1892, till the close of 1893. Before that time he had lectured on the 
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the success of his Essays and his Handbook of Public International Law- 
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In the Principles of International Law, Dr. Lawrence has endeavored 
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intricate questions. His book is divided into four parts. The first deals 
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of Peace, the third with the Law of War, and the fourth with the Law of 
Neutrality. Throughout the work the examples and illustrations are taken 
very largely from British and American history. The table of contents is so 
arranged as to make it an analysis of the subject-matter, and there is an 
index of cases in addition to the general index. 



666 pages, small octavo, $3.00. 



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